Document:

<PAGE>   1
                                                                   EXHIBIT 10.20

                              ASSUMPTION AGREEMENT

        THIS ASSUMPTION AGREEMENT is executed and delivered pursuant to that
certain Agreement and Plan of Merger, dated as of January 28, 2001 (the "Merger
Agreement"), by and among Maxim Integrated Products, Inc., a Delaware
corporation (the "Company"), MI Acquisition Sub, Inc., a Delaware corporation,
and Dallas Semiconductor Corporation, a Delaware corporation ("Dallas
Semiconductor"), pursuant to which Dallas Semiconductor will become a wholly
owned subsidiary of the Company. Pursuant to Section 6.3(c) of the Merger
Agreement, the Company is required to expressly assume the obligations of that
certain Split-Dollar Insurance Agreement, dated as of January 23, 2001, by and
between M. D. Sampels and Dallas Semiconductor, as amended ("Split-Dollar
Agreement"), a copy of which is attached hereto as Exhibit A.

        For good and valuable consideration, the receipt and sufficiency of
which is hereby acknowledged, in accordance with the provisions of Section 14(a)
of the Split-Dollar Agreement, the Company hereby assumes and agrees to pay,
perform and discharge in accordance with the terms thereof, all of the duties,
liabilities and obligations of Dallas Semiconductor under the Split-Dollar
Agreement.

        This Assumption Agreement shall be binding upon and inure to the benefit
of the parties hereto and their respective successors and assigns.

      [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK; SIGNATURE PAGE FOLLOWS]

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        IN WITNESS WHEREOF, each party hereto has caused this instrument to be
        executed by its duly authorized officer this the 11th day of April,
        2001.

                                        MAXIM INTEGRATED PRODUCTS, INC.

                                        By:   /s/ Carl W. Jasper
                                            ------------------------------------
                                        Name:  Carl W. Jasper
                                        Title: Chief Financial Officer

                                        DALLAS SEMICONDUCTOR CORPORATION

                                        By:   /s/ Alan P. Hale
                                            ------------------------------------
                                        Name:  Alan P. Hale
                                        Title: Chief Financial Officer

                                       2
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                                    EXHIBIT A

                                       3
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                        DALLAS SEMICONDUCTOR CORPORATION
                        SPLIT-DOLLAR INSURANCE AGREEMENT

        THIS AGREEMENT is entered into as of this 20th day of July, 2000, by
and between Merlyn D. Sampels ("Participant"), whose address is 7718 Caruth
Boulevard, Dallas, Texas 75225, and Dallas Semiconductor Corporation, a Delaware
corporation ("Company"), having its principal office and place of business
located at 4401 South Beltwood Parkway, Dallas, Texas 75244.

        WHEREAS, the Company by resolution of the Board of Directors duly
adopted on December 17, 1993 ("Date of Adoption") has adopted the Dallas
Semiconductor Corporation Split-Dollar Insurance Plan to promote the interests
of the Company in retaining the officers and directors of the Company who have
made, and are capable of continuing to make, valuable contributions to the
Company's performance by providing life insurance protection; and

        WHEREAS, Participant is a director of the Company who had completed at
least five (5) years of service as a director of the Company on the Date of
Adoption and has expressed a willingness to continue his services as a director
of the Company, or is an officer of the Company at the Vice President level or
above on the Date of Adoption; and

        WHEREAS, Participant entered into an agreement with the Company dated
the 15th day of February, 1994, concerning a split-dollar life insurance
arrangement with the Company (the "Prior Agreement"); and

        WHEREAS, this Agreement amends, restates and supersedes in its entirety
the terms of the Prior Agreement, effective the date of this Agreement;

        NOW, THEREFORE, the parties hereto agree as follows:

        1. Policy. Participant has applied for, and the Company has caused to be
issued, a policy or policies of permanent life insurance described on Exhibit
"A" attached hereto, with the attributes described in Section 2 hereof (such
policy or policies, together with any additional policy or policies issued with
the consent of Participant in substitution or replacement for any such policy or
policies, are collectively referred to herein as the "Policy") from an insurance
company selected by the Company as described on Exhibit "A" ("Insurer"). The
Participant has also applied for and the Company has caused to be issued a
policy or policies of permanent life insurance in which another Plan participant
is the named insured, such policy being identified on Exhibit "A" as the
Nationwide Policy. The term "Policy" shall also include such policy. The Company
will take all such action as may be necessary or appropriate to cause the Policy
to be maintained in force at all times, so as to provide Participant with all of
the benefits of the Policy and this Agreement.

<PAGE>   5

        2. Benefits. The Policy has been structured, based on a specified
interest rate, mortality and other assumptions, to provide Participant (over and
above benefits payable to the Company) with the benefits, during each year in
which the Policy is in force, provided in the Policy and those benefits
described on Exhibit "A" attached hereto. The Company assumes no responsibility
or liability with respect to the actual performance of the Policy, but the
Company agrees to timely pay to the insurer such amounts as may be needed for
the cash value in Nationwide Policy No. N056117510 to always be at least
$250,000.

        3. Ownership of Policy. With respect to any Policy, the Participant (or
if Participant so elects, an individual or entity designated by Participant)
shall be the owner of the Policy, and the Participant, subject to the limited
collateral assignment of such Policy to the Company as provided in Section 7
hereof, may exercise all the rights of ownership with respect to the Policy,
including, but not limited to: (a) the right to designate, or change the
designation of, any beneficiary or beneficiaries of the Policy, (b) the right to
pledge the Policy as security for a loan or to obtain from the Insurer a loan
against the surrender or cash value, and in accordance with the terms, of the
Policy, (c) the right to withdraw, during the Participant's lifetime, all or any
part of the Policy's cash value (specifically including the cash value in
Nationwide Policy No. 56117510) on the date of Participant's withdrawal, (d) the
right to assign or transfer the Policy, in whole or in part, and (e) the right
to sell, surrender or terminate the Policy.

        4. Payment of Premiums. All premiums on the Policy shall be paid by the
Company (or in the discretion of the Company, on behalf of the Company by the
trustee [the "Trustee"] of the Dallas Semiconductor Corporation Executive
Split-Dollar Insurance Trust [the "Trust"]). The Company shall never permit the
Policy to lapse. Premium payments paid by the Trustee shall be considered as
payments by the Company for all purposes under this Agreement. While all
premiums on the Policy shall be paid by or on behalf of the Company, that
portion of the premium equal to the amount of income imputed to Participant for
federal and state income tax purposes on the value of the economic benefit of
the life insurance protection provided to Participant shall be deemed to have
been paid by the Company to the Participant and immediately paid by Participant
to the Insurer. If the Company elects to pay the premiums to the Trust, such
payment shall constitute sufficient funds to pay all premiums which may become
due on each such Policy.

        5. Change of Control. In the event of the occurrence of a Change of
Control (as hereinafter defined): (a) the Company (or if so directed by the
Company, the Trustee) shall immediately pay to the Insurer all remaining
premiums on the Policy, regardless of whether such premiums are then due, and
(b) the collateral assignment of the Policy to the Company, as provided in
Section 7 hereof shall immediately and fully terminate, and the Participant
shall become fully vested in the entire cash value and death benefit payable
under the Policy. For purposes of this Agreement, a "Change in Control" shall
mean a change in control of a nature that would be required to be reported in
response to Item 6(e) of Schedule 14A of Regulation 14A promulgated under the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), whether or not
the Company is then subject to such reporting requirement; provided that,
without limitation, such a Change in Control shall be deemed to have occurred if
(i) any "person" (as such term is used in Sections 13(d) and 14(d) of the
Exchange Act) is or becomes the "beneficial owner" (as defined in Rule 13d-3
under the Exchange Act), directly or indirectly, of securities of

                                       2
<PAGE>   6

the Company representing 15% or more of the combined voting power of the
Company's then outstanding securities; (ii) at any time following the date of
execution of this Agreement individuals who are directors of the Company at such
date cease for any reason to constitute a majority of the Board of Directors;
(iii) the stockholders of the Company approve a merger or consolidation of the
Company with any other corporation, other than a merger or consolidation which
would result in the voting securities of the Company outstanding immediately
prior thereto continuing to represent (either by remaining outstanding or by
being converted into voting securities of the surviving entity) more than 80% of
the combined voting power of the voting securities of the Company or such
surviving entity outstanding immediately after such merger or consolidation,
except that a merger or consolidation effected to implement a recapitalization
of the Company (or similar transaction) in which no "person" (as hereinabove
defined) acquires more than 15% of the combined voting power of the Company's
then outstanding securities shall not constitute a Change in Control of the
Company; (iv) the stockholders of the Company approve a plan of complete
liquidation of the Company or an agreement for the sale or disposition by the
Company of all or substantially all of the Company's assets; or (v) the election
of any person other than C. V. Prothro as Chairman of the Board and Chief
Executive Officer of the Company.

        6. Tax Offset Payments. To the extent that the Participant may be deemed
to have realized gross income in any year for federal and state income tax
purposes or gift tax purposes by reason of this Agreement, including the value
of the insurance protection or other benefits thereunder provided by the Policy
or otherwise as a consequence of the Plan (including, but not limited to the
vesting of benefits to the Participant upon the occurrence of a Change of
Control or otherwise), the Company shall pay to Participant an additional amount
such that the after-tax cost to the Participant is zero.

        7. Collateral Assignment of Policy. The Participant shall, and does
hereby, collaterally assign to the Company an interest in the cash values and
death benefit of the Policy as follows:

               (a) If the Participant surrenders or sells the Policy, he shall
        pay the Company, out of the proceeds of the Policy, an amount equal to
        the lesser of (i) the cash value of the Policy, or (ii) the aggregate
        amount of premiums paid by the Company with respect to the Policy;

               (b) The Company shall be entitled to receive the cumulative
        premiums paid for MetLife Policies Nos. 940250361 E3 and 940250367 E3
        (the amount of which is a portion of the amount indicated in the column
        headed Death Benefits Payable to the Company shown on Exhibit "A"
        attached hereto) from the death benefit paid under Nationwide Policy No.
        N056117510, and the Company shall be entitled to receive the cumulative
        premiums paid for John Hancock Policy No. 534889 (the amount of which is
        the remainder of the amount indicated in the column headed Death
        Benefits Payable to the Company shown on Exhibit "A" attached hereto)
        from the death benefits payable under such policy upon the death of the
        survivor of the insured covered under such policy. All death benefits
        payable under MetLife Policies Nos. 940250361 E3 and 940250367 E3 shall
        be paid to the beneficiary or beneficiaries of the Participant, and all

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        death benefits payable under John Hancock Policy No. 534889 that exceed
        the premiums reimbursed to the Company out of such policy's proceeds
        under the preceding sentence shall be paid to the beneficiary or
        beneficiaries of Participant. (The death benefits payable under the
        MetLife policies are indicated in the column headed Death Benefit
        Payable to Participant's Beneficiary: Individual Coverage, and the death
        benefits payable under the John Hancock policy are indicated in the
        column headed Death Benefit Payable to Participant's Beneficiary:
        Survivorship Coverage, both columns as shown on Exhibit "A" attached
        hereto.) All death benefits payable under Nationwide Policy No.
        N056117510 that exceed the premiums reimbursed to the Company out of
        such policy's proceeds under the first sentence of this paragraph shall
        be paid as follows: (1) to Participant's beneficiary or beneficiaries,
        the excess of (A) 1,300,000 over (B) the amounts, if any, paid to
        Participant, in Participant's sole discretion, from Nationwide Policy
        No. N056117510 during Participant's lifetime, and (2) the balance to the
        Company. If the death benefits payable under this Agreement exceed the
        sum of (i) the aggregate amount of premiums paid by the Company as set
        forth on Exhibit "A" and (ii) the other amounts payable to the Company
        under this paragraph, such excess death benefits shall be payable to the
        Participant's beneficiary or beneficiaries.

        The collateral assignment of the Policy shall not be altered or changed
without the consent of the Company and the Participant.

        8. Adjustment of Benefits; Additional Policy Benefits or Riders. The
Company and the Participant may from time to time enter into agreements which
may adjust the value of each party's interests in the Policy. The Participant
may add any rider or endorsement to the Policy. If any such rider or endorsement
is added upon the written request of the Company, all premiums with respect to
such rider or endorsement shall be paid by the Company. A Participant shall not
be required to withdraw any benefits payable under the Policy and may elect to
apply the value attributable to such benefits to the purchase of additional
benefits payable to the beneficiary or beneficiaries named by Participant under
the Policy, if the Participant so elects, or to treat such benefits as
additional insurance payable to the beneficiary or beneficiaries of such Policy
upon the death of the Participant.

        9. Amendment. This Agreement may be amended by the Board of Directors of
the Company; provided, however, that no such amendment shall diminish, abrogate
or change any rights or benefits of the Participant under the Policy or this
Agreement without the Participant's prior written consent, and no amendment of
the Policy or this Agreement shall be made upon or after the occurrence of a
Change of Control without the prior written consent of each Participant.

        10. Benefits Cumulative. The benefits to the Participant under this
Agreement shall be cumulative with, and shall not reduce or be deemed to be in
substitution of, any benefits, payments or compensation to which Participant may
otherwise be entitled under any other compensation, benefit, welfare, savings,
retirement or compensation plan of, or for the employees, officers or directors
of, the Company.

        11. Further Assurances. The Company and Participant shall enter into,
execute and deliver all such documents, instruments, and other agreements as the
other party may reasonably

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request, or as the Insurer or Participant may reasonably require, in order to
carry out the intent and purposes of this Agreement.

        12. ERISA Requirements.

        (a) Funding Policy. All premiums on the Policy shall be remitted by, or
on behalf of, the Company to the Insurer. The benefits provided by the Policy
shall be paid by the Insurer in accordance with the terms of the Policy and this
Agreement. The payment of such benefits is predicated on the payment of the
required premiums.

        (b) Claims and Review Procedures. The following claims procedure shall
apply for purposes of this Agreement. The claims procedure in subparagraph
(b)(1) below shall be followed with respect to benefits provided by the Insurer
under the terms of the Policy. The claims procedure in subparagraph (b)(2) below
shall be followed with respect to benefits, if any, provided directly by the
Company. The Participant (or the other owner of the Policy designated by the
Participant) that owns the Policy (the "Policy Owner") and the Policy Owner's
successors, beneficiaries or representatives, as appropriate (individually or
collectively, "Claimant"), must follow both procedures, if necessary.

               (i) Filing a Claim for Insurance Benefits. A Claimant shall make
        a claim for benefits provided by the Insurer by submitting a written
        claim and proof of claim to the Insurer in accordance with procedures
        and guidelines established from time to time by the Insurer. On written
        request, the Company, acting as the "Plan Administrator," shall provide
        copies of any claim forms or instructions, or advise the Claimant how to
        obtain such forms or instructions. The Insurer shall decide whether the
        claim shall be allowed. If a claim is denied in whole or in part, the
        Insurer shall notify the Claimant and explain the procedure for
        reviewing a denied claim.

               (ii) Filing a Claim for Any Other Benefit. The following claims
        procedure shall apply with respect to all benefits other than those
        provided by the Insurer:

                      (A) Filing a Claim; Notification to Claimant of Decision:
               The Claimant shall make a claim in writing in accordance with
               procedures and guidelines established from time to time by the
               Plan Administrator, which claim shall be delivered to the Plan
               Administrator. The Plan Administrator shall review and make the
               decision with respect to any claim. If a claim is denied in whole
               or in part, written notice thereof shall be furnished to the
               Claimant within thirty days after the claim has been filed. Such
               notice shall set forth:

                             (1) the specific reason or reasons for the denial;

                             (2) specific reference to the provisions of this
                      Agreement on which denial is based;

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                             (3) a description of any additional material or
                      information necessary for the Claimant to perfect a claim
                      and an explanation of why such material or information is
                      necessary; and

                             (4) an explanation of the procedure for review of
                      the denied claim.

                      (B) Procedure for Review: Any Claimant whose claim has
               been denied in full or in part may individually, or through the
               Claimant's duly authorized representative, request a review of
               the claim denial by delivering a written application for review
               to the Plan Administrator at any time within sixty days after
               receipt by the Claimant of written notice of the denial of the
               claim. Such request shall set forth in reasonable detail:

                             (1) the grounds upon which the request for review
                      is based and any facts in support thereof; and

                             (2) any issues or comments which the Claimant
                      considers pertinent to the claim.

                      Following such request for review, the Plan Administrator
               fully and fairly shall review the decision denying the claim.
               Prior to the decision of the Plan Administrator, the Claimant
               shall be given an opportunity to review pertinent documents.

                      (C) Decision on Review: A decision on the review of a
               claim denied in whole or in part shall be made in the following
               manner:

                             (1) The decision on review shall be made by the
                      Plan Administrator, which shall consider the application
                      and any written materials submitted by the Claimant in
                      connection therewith. The Plan Administrator, in its sole
                      discretion, may require the Claimant to submit such
                      additional documents or evidence as the Plan Administrator
                      may deem necessary or advisable in making such review.

                             (2) The Plan Administrator will render a decision
                      upon a review of a denied claim within sixty days after
                      receipt of a request for review. If special circumstances
                      (such as the need to hold a hearing on any matter
                      pertaining to the denied claim) warrant additional time,
                      the decision will be rendered as soon as possible, but not
                      later than one hundred twenty days after receipt of a
                      request for review. Written notice of any such extension
                      will be furnished to the Claimant prior to the
                      commencement of the extension.

                             (3) The decision on review shall be in writing and
                      shall include specific reasons for the decision, written
                      in a manner calculated to be

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                      understood by the Claimant, and specific references to the
                      provisions of this Agreement on which the decision is
                      based. The decision of the Plan Administrator on review
                      shall be final and conclusive upon all persons. If the
                      decision on review is not furnished to the Claimant within
                      the time limits prescribed in subparagraph (c)(2) above,
                      the claim will be deemed denied on review.

        13. Legal Fees. The Company shall pay to the Participant and his
beneficiary and beneficiaries upon demand all legal fees and expenses incurred
by the Participant or by his beneficiary or beneficiaries, respectively, in
seeking to obtain or enforce any right or benefit provided by the Policy and
this Agreement.

        14. Successors; Binding Agreement.

        (a) In addition to the requirements of Section 5 of this Agreement, the
Company will, upon the request of Participant, require any proposed successor
(whether direct or indirect, by purchase, merger, consolidation or otherwise) to
all or substantially all of the business and/or assets of the Company to
expressly assume and agree to perform this Agreement in the same manner and to
the same extent that the Company would be required to perform it if no such
succession were to take place. Failure of the Company to obtain such assumption
and agreement prior to the effectiveness of any such succession shall be a
breach of this Agreement and shall entitle the Participant to all rights,
compensation and other benefits from the Company in the same amount and on the
same terms as the Participant would otherwise be entitled hereunder. As used in
this Agreement, "Company" shall mean the Company as hereinbefore defined and any
such successor to its business and/or assets as aforesaid, by operation of law,
or otherwise.

        (b) Subject to the provisions of Section 14(a) above, the terms and
provisions of this Agreement shall inure to the benefit of and be binding upon
(a) the Company and its successors and assigns and (b) the Participant and his
respective heirs, executors, administrators and legal representatives.

        15. Validity. The invalidity or unenforceability of any provision of
this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement, which shall remain in full force and effect.

        16. Miscellaneous. No waiver by either party hereto at any time of any
breach by the other party hereto of, or compliance with, any condition or
provision of this Agreement to be performed by such other party shall be deemed
a waiver of similar or dissimilar provisions or conditions at the same or at any
prior or subsequent time. No agreements or representations, oral or otherwise,
express or implied, with respect to the subject matter hereof have been made by
either party which are not expressly set forth in this Agreement. The validity,
interpretation, construction and performance of this Agreement shall be governed
by the laws of the State of Delaware. All references to sections of the Exchange
Act or the Code shall be deemed also to refer to any successor provisions to
such sections. The obligations of the Company under this Agreement shall survive
the expiration of this Agreement.

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<PAGE>   11

        17. Notice. For the purpose of this Agreement, notices and all other
communications provided for in the Agreement shall be in writing and shall be
deemed to have been duly given when delivered or mailed by United States
registered mail, return receipt requested, postage prepaid, addressed to the
respective addresses set forth on the first page of this Agreement, provided
that all notices to the Company shall be directed to the attention of the Chief
Executive Officer with a copy to the Chief Financial Officer, or to such other
address as either party may have furnished to the other in writing in accordance
herewith, except that notice of change of address shall be effective only upon
receipt.

        18. Indemnification.

        (a) The Company hereby agrees to indemnify and hold harmless the
Participant and any beneficiary or beneficiaries of Participant against any and
all expenses (including attorneys' fees), judgments, fines and amounts paid in
settlement, actually and reasonably incurred by Participant or any beneficiary
or beneficiaries or Participant in connection with any threatened, pending or
completed action, suit, or proceeding, whether formal or informal, or civil,
criminal, administrative, legislative, arbitrative or investigative (hereinafter
a "Proceeding") to which the Participant or any beneficiary or beneficiaries of
Participant is, was, or at any time becomes a party, or is threatened to be made
a party, in any way arising out of, based upon or incident to this Agreement or
any of the rights, benefits and obligations provided for herein.

        (b) The expenses (including attorneys' fees) incurred by Participant or
any beneficiary or beneficiaries of Participant in defending any Proceeding
shall be advanced by the Company at the request of the Participant or any such
beneficiary or beneficiaries. Any judgments, fines or amounts to be paid in
settlement shall also be advanced by the Company to the Participant or any
beneficiary or beneficiaries of Participant upon request.

        19. Governing Law. This Agreement shall be governed and construed in
accordance with the laws of the State of Delaware.

        20. Headings. Headings in this Agreement are inserted for reference and
convenience only and shall not be deemed a part of this Agreement.

        21. Counterparts. This Agreement may be executed in several
counterparts, each of which shall be deemed to be an original but all of which
together will constitute one and the same instrument.

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<PAGE>   12

        IN WITNESS WHEREOF, the parties hereto have entered into this Agreement
as of the 20th day of July, 2000.

                                        DALLAS SEMICONDUCTOR CORPORATION

                                        By:    /s/ C. V. Prothro
                                            ------------------------------------

                                               /s/ Merlyn D. Sampels
                                        ----------------------------------------
                                               Merlyn D. Sampels, Participant

                                       9
<PAGE>   13

                                   EXHIBIT "A"

NAME OF PARTICIPANT:    Merlyn Sampels

NAME OF INSURED:        Merlyn Sampels & Anita Sampels

INSURER:                MetLife Policy No. 940 250 361 E3 & 940 250 367 E3

INSURER:                John Hancock Policy No. 20 050 266

INSURER:                Nationwide Policy No. N056117510

<TABLE>
<CAPTION>
                    Death Benefit             Death Benefit
                    Payable to Participant's  Payable to Participant's   Death Benefit
Policy Year         Beneficiary:              Beneficiary:               Payable to
Ending April 15     Individual Coverage       Survivorship Coverage      Company
---------------     -------------------       ---------------------      -------
<S>                 <C>                       <C>                        <C>
2001                3,246,991                 3,735,000                  5,519,000
2002                3,293,365                 3,678,000                  5,914,000
2003                3,342,192                 3,759,354                  6,309,000
2004                3,390,719                 4,001,519                  6,541,657
2005                3,438,994                 4,001,519                  6,671,285
2006                3,489,342                 4,001,519                  6,801,284
2007                3,542,630                 4,001,519                  6,931,284
2008                3,450,183                 4,001,519                  3,877,657
2009                3,362,307                 4,001,519                  3,877,657
2010                3,281,168                 4,001,519                  3,877,657
2011                3,204,682                 4,001,519                  3,877,657
2012                3,132,924                 4,001,519                  3,747,382
2013                1,755,900                 4,001,519                  3,747,097
2014                1,724,966                 4,001,519                  3,746,804
2015                1,674,852                 4,001,519                  3,746,501
2016                1,623,153                 4,001,519                  2,848,531
2017                1,570,472                 4,001,519                  2,848,208
2018                1,516,905                 4,001,519                  2,848,874
2019                1,462,431                 4,001,519                  2,848,530
2020                1,406,824                 4,001,519                  2,847,174
</TABLE>

                                       10
<PAGE>   14

                                  AMENDMENT TO
                        DALLAS SEMICONDUCTOR CORPORATION
                        SPLIT-DOLLAR INSURANCE AGREEMENT

        THIS AMENDMENT TO DALLAS SEMICONDUCTOR CORPORATION SPLIT-DOLLAR
INSURANCE AGREEMENT is entered into as of this 23rd day of January, 2001, by and
between Merlyn D. Sampels ("Participant") and Dallas Semiconductor Corporation,
a Delaware corporation ("Company").

        WHEREAS, Participant entered into a Split-Dollar Insurance Agreement
with the Company dated July 20, 2000 ("Agreement"); and

        WHEREAS, the Company desires to amend the Agreement in the manner set
forth below and has requested the consent of Participant to such amendment;

        NOW, THEREFORE, in consideration of the payment by the Company to
Participant of the sum of $10.00 and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged by Participant,
Participant and the Company agree as follows:

        1. Section 4. Section 4 is divided into subsections (a) and (b).
Existing Section 4 entitled "Payment of Premiums" is designated as Section 4(a),
and the following language is inserted as Section 4(b):

               "(b) All premiums on the Policy shall be paid upon request or
        demand by Participant or Participant's Insurer without regard to whether
        or not the Participant is an employee or director of the Company, the
        Participant's responsibilities to the Company or any other circumstance,
        such obligation to pay to be absolute, continuing, irrevocable and
        unconditional and not subject to any set-off, counterclaim, recoupment,
        reduction, diminution or any defense of any kind or nature whatsoever."

        2. Section 5. Section 5 is deleted in its entirety and the following is
substituted in its place:

               "Reserved."

        3. Section 6. The words "(including, but not limited to the vesting of
benefits to the Participant upon the occurrence of a Change of Control or
otherwise)" appearing in lines 4, 5 and 6 of Section 6 are deleted.

        4. Section 9. The words "and no amendment of the Policy or this
Agreement shall be made upon or after the occurrence of a Change of Control
without the prior written consent of each Participant" found in lines 4 and 5 of
Section 9 are deleted.

        5. Section 14. Subsection (a) of Section 14 is amended to delete the
words "In addition to the requirements of Section 5 of this Agreement" appearing
in line 1 thereof.

<PAGE>   15

        IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the 23rd day of January, 2001.

                                        DALLAS SEMICONDUCTOR CORPORATION

                                        By:    /s/ Chao C. Mai
                                            ------------------------------------

                                               /s/ Merlyn D. Sampels
                                        ----------------------------------------
                                        Merlyn D. Sampels, Participant

                                       2<PAGE>   1
                                                                   EXHIBIT 10.21

                             SHAREHOLDER'S AGREEMENT

        THIS AGREEMENT is made as of the ___ day of ________________, 19__, by
and between DALLAS SEMICONDUCTOR CORPORATION, a Delaware corporation (the
"Company"), and _________________________________ (the "Purchaser").

        WHEREAS, the Purchaser has been granted an option under the Company's
1987 Stock Option Plan to purchase shares of Common Stock, $.02 par value per
share (the "Common Stock"), of the Company; and

        WHEREAS, the Purchaser and the Company desire to set forth certain
rights and obligations of the parties with respect to the Common Stock which may
from time to time be purchased by the Purchaser;

        NOW, THEREFORE, IT IS HEREBY AGREED:

        1. Sale and Purchase of Shares. Pursuant to the terms and conditions of
this Agreement, the Purchaser has been granted an option to purchase up to
______ shares of the Common Stock of the Company (the "Shares") for a
consideration of $_________ per share to be paid by Purchaser to the Company
upon exercise of such option in accordance with the terms of such option.

        2. Company's Right to Repurchase. The Shares shall be subject to the
following right ("Repurchase Right"):

               (a) If the Purchaser should cease to be employed by the Company,
for any reason or no reason, with or without cause, as determined by and in the
sole discretion of the Board of Directors of the Company (excluding leave(s) of
absence authorized in writing by the Company, specifying the date on which
Purchaser shall return to work), the Company shall have the right to repurchase
from the Purchaser, or the Purchaser's personal representative as the case may
be, all of the Shares subject to the Repurchase Right. For purposes of
determining this Repurchase Right, the parties hereby acknowledge and agree that
the Commencement Date (as used herein) with respect to the Shares shall be
deemed to be _________________, 19__.

               (b) The percentage of the Shares which are subject to the
Repurchase Right shall be determined as follows:

<TABLE>
<CAPTION>
                  Length of Time Employee
                  Has Been Employed by the                  Percentage of
                     Company Since the                    Shares Subject to
                     Commencement Date                    Repurchase Right
                     -----------------                    ----------------
<S>                                                       <C>
               Less than 4 completed quarters                    100%
               4 completed quarters                               75%
               5 completed quarters                            68.75%
               6 completed quarters                            62.50%
</TABLE>

<PAGE>   2

<TABLE>
<CAPTION>
                  Length of Time Employee
                  Has Been Employed by the                  Percentage of
                     Company Since the                    Shares Subject to
                     Commencement Date                    Repurchase Right
                     -----------------                    ----------------
<S>                                                       <C>
               7 completed quarters                            56.25%
               8 completed quarters                               50%
               9 completed quarters                            43.75%
               10 completed quarters                           37.50%
               11 completed quarters                           31.25%
               12 completed quarters                              25%
               13 completed quarters                           18.75%
               14 completed quarters                           12.50%
               15 completed quarters                            6.25%
               16 or more completed quarters                     None
</TABLE>

A completed quarter excludes the specified time during which Purchaser is on any
approved leave(s) of absence and the measurement of time from the Commencement
Date shall abate during such specified time.

               (c) Within sixty (60) days after the later of the date when
Purchaser's active employment ceases or the date any approved leave terminates,
Purchaser having failed to return to work within the time specified (the
"Termination Date"), upon notice to Purchaser specifying the time, place and
date for settlement, the Company may, at the Company's option, repurchase from
the Purchaser, in cash, the Shares which are subject to the Repurchase Right at
a total price equal to Purchaser's original purchase price per share as set
forth in Paragraph 1 above. If the Company expressly elects not to exercise its
Repurchase Right, or fails to exercise its Repurchase Right for whatever reason
with respect to such shares within such sixty day period, the Company's
Repurchase Right with respect to such shares shall expire.

               (d) The Purchaser understands that he Is an employee at will and
that nothing in this Agreement shall interfere with or limit in any manner
whatsoever the right or power of the Company to terminate Purchaser's employment
with or without cause.

        3. Rights as Stockholder; Escrow.

               (a) From and after the date of issuance of the Shares and subject
to the terms and conditions of this Agreement, the Purchaser shall have all of
the rights of a stockholder of the Company with respect to the Shares unless and
until repurchased by the Company as provided hereinbefore or other disposition
of the Shares by Purchaser in accordance with the provisions of this Agreement.

               (b) The parties hereby agree that all certificates representing
the Shares shall be held by either the Secretary of the Company or in an
appropriate safekeeping account maintained by the Company with a bank or other
financial institution ("Agent"). The Purchaser shall deliver to the Secretary of
the Company, for each such certificate, a duly executed stock power authorizing
any officer of the Company to effect the transfer of such Shares on the books

<PAGE>   3

of the Company in accordance with the terms of this Agreement. Upon the written
request of Purchaser delivered to the Secretary of the Company, the Company will
cause the Secretary or the Agent to deliver to Purchaser a certificate or
certificates representing such number of Shares as are not then subject to the
Repurchase Right. Within five business days after the exercise or lapse without
exercise of the Repurchase Right, the Company will direct the Secretary or the
Agent to deliver to Purchaser a certificate or certificates representing the
aggregate number of Shares, if any, not repurchased by the Company.

        4. Stock Splits, Recapitalizations, Etc. In the event of any of the
following:

               (a) Any stock dividend, stock split, reverse stock split, share
combination, exchange of shares, recapitalization or other change in the
character or amount of the outstanding securities of the Company; or

               (b) Any consolidation, separation, reorganization, liquidation,
merger, sale of all, or substantially all, of the assets of the Company or like
event or transaction;

then any and all new, substituted or additional securities or property to which
the Purchaser is entitled by reason of ownership of the Shares shall be
immediately subject to this Agreement and be included in the term "Shares" for
all purposes of this Agreement, and the repurchase price per share specified in
Paragraph 2(c) shall be appropriately adjusted by the Board of Directors of the
Company.

        5. Purchase of Additional Stock. If the Purchaser at any time after the
date of this Agreement acquires any capital stock of the Company, in addition to
that described in Paragraphs 1 and 4 above (other than capital stock acquired on
the open market and capital stock acquired from the Company which the Board of
Directors of the Company, in its sole discretion, expressly designates as not
being subject to this Agreement), or any options, rights or warrants therefor
("Additional Stock"), such Additional Stock shall be immediately subject to this
Agreement and included in the term "Shares" for all purposes of this Agreement;
provided, however, that:

               (a) The repurchase price per share of such Additional Stock shall
be the purchase price per share paid or to be paid by the Purchaser therefor;

               (b) Any such Additional Stock purchased pursuant to an option
that conditions the right to exercise all or part of such option upon the
passage of an amount of time in excess of three (3) years shall be deemed to be
fully vested and not subject to the Repurchase Right; and

               (c) The Commencement Date for purposes of the Repurchase Right
with respect to such Additional Stock shall be the date expressly designated as
such by the Board of Directors of the Company, in its sole discretion, or absent
such a designation shall be, in the case of Additional Stock acquired pursuant
to the exercise of an option, warrant or similar right, the date of grant of
such option, warrant or right, or, in the case of Additional Stock otherwise
purchased from the Company, the date of such purchase.

<PAGE>   4

        6. Investment Representations by Purchaser. The purchase of the Shares
and any Additional Stock shall be subject to the condition that, if required by
the Board of Directors of the Company, in its sole discretion, the Purchaser
shall make each of the following representations:

               (a) That Purchaser is acquiring the Shares with his own funds and
not with a view to the sale or distribution of any part thereof, and that
Purchaser has no present intention of selling, granting any participation in or
otherwise distributing the same.

               (b) That Purchaser has no contract, undertaking, agreement or
arrangement of any kind to sell, transfer or grant participations to any third
person with respect to the Shares or any part thereof.

               (c) That Purchaser has such knowledge and experience in financial
and business matters as to be capable of evaluating the merits and risks of his
investment and is able to fend for himself in the transaction contemplated by
this Agreement. That Purchaser has the ability to bear the economic risks of his
investment and has been furnished with and has had access to such information as
would be made available in the form of a registration statement, together with
such additional information as is necessary to verify the accuracy of the
information supplied and to have all questions answered by the Company.

               (d) That Purchaser is familiar with Rule 144 under the Securities
Act of 1933, as amended (the "Act"), and understands that the Shares constitute
"restricted securities" within the meaning of that Rule. That sale of the Shares
may be made only after completing certain forms of representation letters
promulgated for such sales, which may be obtained from the Secretary of the
Company. That Purchaser understands that any sale of the Shares which might be
made by him in reliance upon Rule 144 may be made only in limited amounts in
accordance with the terms and conditions of that Rule and that he may not be
able to sell the Shares at the time or in the amount Purchaser so desires.

               (e) Such other representations and warranties as the Company may,
in its discretion, require.

               The parties hereby acknowledge, however, that such
representations shall be deemed inapplicable to any purchase of Shares, or any
part thereof, made in accordance with the terms of a registration statement
covering such purchase, which has been filed and has become effective under the
Act, and with respect to which no stop order suspending the effectiveness
thereof has been issued.

        7. Restrictive Legends.

               (a) All certificates representing any Shares subject to the
Repurchase Rights provided for in this Agreement shall have endorsed thereon
substantially the following legend:

               "THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
               THE TERMS AND CONDITIONS OF A CERTAIN SHAREHOLDER'S AGREEMENT
               WHICH, AMONG OTHER

<PAGE>   5

               THINGS, RESTRICTS THE TRANSFER OF SUCH SECURITIES AND GRANTS THE
               CORPORATION THE RIGHT TO REPURCHASE THESE SECURITIES UNDER
               CERTAIN CONDITIONS. COPIES OF SUCH AGREEMENT MAY BE OBTAINED UPON
               WRITTEN REQUEST TO THE SECRETARY OF THE CORPORATION."

               (b) In addition to the foregoing legend, any certificate
representing any shares, other than shares which have been registered with the
Securities and Exchange Commission (the "Commission") pursuant to an effective
registration statement under the Act with respect to which no stop order
suspending the effectiveness thereof has been issued, shall have endorsed
thereon substantially the following legends:

               (i)    "THE SHARES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
                      REGISTERED UNDER THE SECURITIES ACT OF 19331 AS AMENDED
                      (THE ACT") NOR UNDER ANY APPLICABLE STATE LAW, AND SUCH
                      SHARES MAY NOT BE SOLD, TRANSFERRED, ASSIGNED OR OTHERWISE
                      DISPOSED OF UNLESS A REGISTRATION STATEMENT UNDER THE ACT
                      WITH RESPECT TO SUCH DISPOSITION SHALL THEN BE IN EFFECT
                      AND ALL APPLICABLE STATE AND BLUE SKY LAWS HAVE BEEN
                      COMPLIED WITH, OR UNLESS THE PERSON REQUESTING THE
                      TRANSFER OF SUCH SHARES SHALL FURNISH AN OPINION OF
                      COUNSEL (BOTH COUNSEL AND OPINION TO BE SATISFACTORY TO
                      THE CORPORATION) TO THE EFFECT THAT SUCH SALE, TRANSFER,
                      ASSIGNMENT OR DISPOSITION WILL NOT INVOLVE ANY VIOLATION
                      OF THE ACT OR ANY SUPERSEDING STATUTE OR ANY APPLICABLE
                      STATE OR BLUE SKY LAWS."

               (ii)   Any legend required to be placed thereon by applicable
                      state securities laws.

        8. No Obligation to Transfer. The Company shall not be required W to
transfer or have transferred on its books any Shares which shall have been sold
or transferred in violation of any of the provisions set forth in this
Agreement, or (ii) to treat as the owner of such Shares or to accord the right
to vote as such owner or to pay dividends to any transferee to whom such Shares
shall have been so transferred.

        9. Further Assurances. The parties agree to execute such further
instruments and to take such further action as may reasonably be necessary to
carry out the intent of this Agreement.

        10. Notices. Any notice required or permitted hereunder shall be given
in writing and shall be deemed effectively given upon personal delivery or upon
deposit in the United States Post Office, by registered or certified mail, with
postage prepaid, addressed to the other party

<PAGE>   6

hereto at the address shown below his signature or at such other address as such
party may designate from time to time by advance written notice to the other
party hereto.

        11. Governing Law. This Agreement shall be construed, and the provisions
hereof shall be enforced, in accordance with the laws of the State of Delaware.

        12. Assigns. This Agreement shall be binding upon and inure to the
benefit of the Company and its successors and assigns and, subject to the
restrictions set forth herein on Purchaser's transfer of the Shares, shall be
binding upon and inure to the benefit of Purchaser, his heirs, executors,
administrators, guardians, transferees and assigns.

        13. Entire Agreement; Amendments. This Agreement constitutes the entire
agreement of the parties with respect to the subject matter hereof. This
Agreement may be amended, modified or supplemented only by a written agreement
signed by both of the parties hereto.

        14. Titles and Headings. The section titles and headings herein are for
convenience only and are not to be considered in construing or interpreting this
Agreement.

        15. Execution in Counterparts. This Agreement may be executed in any
number of counterparts, each of which shall be deemed for all purposes to be an
original and all of which together shall be deemed for all purposes to be one
agreement.

        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

                                        DALLAS SEMICONDUCTOR CORPORATION

Address for notices:
4350 Beltwood Parkway South
Dallas, Texas  75244

                                        By:
                                            ------------------------------------

                                        PURCHASER

                                        ----------------------------------------

                                        Address:
                                                 -------------------------------

                                        ----------------------------------------

<PAGE>   7

                                 [87SOP/V5-3/89]

                             SHAREHOLDER'S AGREEMENT

        THIS AGREEMENT is made as of the ___ day of _________________, 19__, by
and between DALLAS SEMICONDUCTOR CORPORATION, a Delaware corporation (the
"Company"), and ____________________________ (the "Purchaser").

        WHEREAS, the Purchaser has been granted an option under the Company's
1987 Stock Option Plan to purchase shares of Common Stock, $.02 par value per
share (the "Common Stock"), of the Company; and

        WHEREAS, the Purchaser and the Company desire to set forth certain
rights and obligations of the parties with respect to the Common Stock which may
from time to time be purchased by the Purchaser;

        NOW, THEREFORE, IT IS HEREBY AGREED:

        1. Sale and Purchase of Shares. Pursuant to the terms and conditions of
this Agreement, the Purchaser has been granted an option to purchase up to _____
shares of the Common Stock of the Company (the "Shares") for a consideration of
$___________ per share to be paid by Purchaser to the Company upon exercise of
such option in accordance with the terms of such option.

        2. Company's Right to Repurchase. The Shares shall be subject to the
following right ("Repurchase Right"):

               (a) If the Purchaser should cease to be employed by the Company,
for any reason or no reason, with or without cause, as determined by and in the
sole discretion of the Board of Directors of the Company (excluding leave(s) of
absence authorized in writing by the Company, specifying the date on which
Purchaser shall return to work), the Company shall have the right to repurchase
from the Purchaser, or the Purchaser's personal representative as the ease may
be, all of the Shares subject to the Repurchase Right. For purposes of
determining this Repurchase Right, the parties hereby acknowledge and agree that
the Commencement Date (as used herein) with respect to the Shares shall be
deemed to be ___________________, 20__.

               (b) The percentage of the Shares which are subject to the
Repurchase Right shall be determined as follows:

<TABLE>
<CAPTION>
                  Length of Time Employee
                  Has Been Employed by the                  Percentage of
                     Company Since the                    Shares Subject to
                     Commencement Date                    Repurchase Right
                     -----------------                    ----------------
<S>                                                       <C>
               Less than 4 completed quarters                    100%
               4 completed quarters                               80%
               5 completed quarters                               75%
</TABLE>

<PAGE>   8

<TABLE>
<CAPTION>
                  Length of Time Employee
                  Has Been Employed by the                  Percentage of
                     Company Since the                    Shares Subject to
                     Commencement Date                    Repurchase Right
                     -----------------                    ----------------
<S>                                                       <C>
               6 completed quarters                               70%
               7 completed quarters                               65%
               8 completed quarters                               60%
               9 completed quarters                               55%
               10 completed quarters                              50%
               11 completed quarters                              45%
               12 completed quarters                              40%
               13 completed quarters                              35%
               14 completed quarters                              30%
               15 completed quarters                              25%
               16 completed quarters                              20%
               17 completed quarters                              15%
               18 completed quarters                              10%
               19 completed quarters                               5%
               20 or more completed quarters                     None
</TABLE>

A completed quarter excludes the specified time during which Purchaser is on any
approved leave(s) of absence and the measurement of time from the Commencement
Date shall abate during such specified time.

               (c) Within sixty (60) days after the later of the date when
Purchaser's active employment ceases or the date any approved leave terminates,
Purchaser having failed to return to work within the time specified (the
"Termination Date"), upon notice to Purchaser specifying the time, place and
date for settlement, the Company may, at the Company's option, repurchase from
the Purchaser, in cash, the Shares which are subject to the Repurchase Right at
a total price equal to Purchaser's original purchase price per share as set
forth in Paragraph 1 above. If the Company expressly elects not to exercise its
Repurchase Right, or fails to exercise its Repurchase Right for whatever reason
with respect to such shares within such sixty day period, the Company's
Repurchase Right with respect to such shares shall expire.

               (d) The Purchaser understands that he is an employee at will and
that nothing in this Agreement shall interfere with or limit in any manner
whatsoever the right or power of the Company to terminate Purchaser's employment
with or without cause.

        3. Rights as Stockholder; Escrow.

               (a) From and after the date of issuance of the Shares and subject
to the terms and conditions of this Agreement, the Purchaser shall have an of
the rights of a stockholder of the Company with respect to the Shares unless and
until repurchased by the Company as provided hereinbefore or other disposition
of the Shares by Purchaser in accordance with the provisions of this Agreement.

<PAGE>   9

               (b) The parties hereby agree that all certificates representing
the Shares shall be held by either the Secretary of the Company or in an
appropriate safekeeping account maintained by the Company with a bank or other
financial institution ("Agent"). The Purchaser shall deliver to the Secretary of
the Company, for each such certificate, a duly executed stock power authorizing
any officer of the Company to effect the transfer of such Shares on the books of
the Company in accordance with the terms of this Agreement. Upon the written
request of Purchaser delivered to the Secretary of the Company, the Company will
cause the Secretary or the Agent to deliver to Purchaser a certificate or
certificates representing such number of Shares as are not then subject to the
Repurchase Right. Within five business days after the exercise or lapse without
exercise of the Repurchase Right, the Company will direct the Secretary or the
Agent to deliver to Purchaser a certificate or certificates representing the
aggregate number of Shares, if any, not repurchased by the Company.

        4. Stock Splits, Recapitalizations, Etc. In the event of any of the
following:

               (a) Any stock dividend, stock split, reverse stock split, share
combination, exchange of shares, recapitalization or other change in the
character or amount of the outstanding securities of the Company; or

               (b) Any consolidation, separation, reorganization, liquidation,
merger, sale of all, or substantially all, of the assets of the Company or like
event or transaction;

then any and all new, substituted or additional securities or property to which
the Purchaser is entitled by reason of ownership of the Shares shall be
immediately subject to this Agreement and be included in the term "Shares" for
all purposes of this Agreement, and the repurchase price per share specified in
Paragraph 2(c) shall be appropriately adjusted by the Board of Directors of the
Company.

        5. Purchase of Additional Stock. If the Purchaser at any time after the
date of this Agreement acquires any capital stock of the Company, in addition to
that described in Paragraphs 1 and 4 above (other than capital stock acquired on
the open market and capital stock acquired from the Company which the Board of
Directors of the Company, in its sole discretion, expressly designates as not
being subject to this Agreement), or any options, rights or warrants therefor
("Additional Stock"), such Additional Stock shall be immediately subject to this
Agreement and included in the term "Shares" for an purposes of this Agreement;
provided, however, that:

               (a) The repurchase price per share of such Additional Stock shall
be the purchase price per share paid or to be paid by the Purchaser therefor;

               (b) Any such Additional Stock purchased pursuant to an option
that conditions the right to exercise all or part of such option upon the
passage of an amount of time in excess of three (3) years shall be deemed to be
fully vested and not subject to the Repurchase Right; and

               (c) The Commencement Date for purposes of the Repurchase Right
with respect to such Additional Stock shall be the date expressly designated as
such by the Board of

<PAGE>   10

Directors of the Company, in its sole discretion, or absent such a designation
shall be, in the case of Additional Stock acquired pursuant to the exercise of
an option, warrant or similar right, the date of grant of such option, warrant
or right, or, in the case of Additional Stock otherwise purchased from the
Company, the date of such purchase.

        6. Investment Representations by Purchaser. The purchase of the Shares
and any Additional Stock shall be subject to the condition that, if required by
the Board of Directors of the Company, in its sole discretion, the Purchaser
shall make each of the following representations:

               (a) That Purchaser is acquiring the Shares with his own funds and
not with a view to the sale or distribution of any part thereof, and that
Purchaser has no present intention of selling, granting any participation in or
otherwise distributing the same.

               (b) That Purchaser has no contract, undertaking, agreement or
arrangement of any kind to sell, transfer or grant participations to any third
person with respect to the Shares or any part thereof.

               (c) That Purchaser has such knowledge and experience in financial
and business matters as to be capable of evaluating the merits and risks of his
investment and is able to fend for himself in the transaction contemplated by
this Agreement. That Purchaser has the ability to bear the economic risks of his
investment and has been furnished with and has had access to such Information as
would be made available in the form of a registration statement, together with
such additional information as is necessary to verify the accuracy of the
information supplied and to have all questions answered by the Company.

               (d) That Purchaser is familiar with Rule 144 under the Securities
Act of 1933, as amended (the "Act"), and understands that the Shares constitute
"restricted securities" within the meaning of that Rule. That sale of the Shares
may be made only after completing certain forms of representation letters
promulgated for such sales, which may be obtained from the Secretary of the
Company. That Purchaser understands that any sale of the Shares which might be
made by him in reliance upon Rule 144 may be made only in limited amounts in
accordance with the terms and conditions of that Rule and that he may not be
able to sell the Shares at the time or in the amount Purchaser so desires.

               (e) Such other representations and warranties as the Company may,
in its discretion, require.

               The parties hereby acknowledge, however, that such
representations shall be deemed inapplicable to any purchase of Shares, or any
part thereof, made in accordance with the terms of a registration statement
covering such purchase, which has been filed and has become effective under the
Act, and with respect to which no stop order suspending the effectiveness
thereof has been issued.

<PAGE>   11

        7. Restrictive Legends.

               (a) All certificates representing any Shares subject to the
Repurchase Rights provided for in this Agreement shall have endorsed thereon
substantially the following legend:

               "THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
               THE TERMS AND CONDITIONS OF A CERTAIN SHAREHOLDER'S AGREEMENT
               WHICH, AMONG OTHER THINGS, RESTRICTS THE TRANSFER OF SUCH
               SECURITIES AND GRANTS THE CORPORATION THE RIGHT TO REPURCHASE
               THESE SECURITIES UNDER CERTAIN CONDITIONS. COPIES OF SUCH
               AGREEMENT MAY BE OBTAINED UPON WRITTEN REQUEST TO THE SECRETARY
               OF THE CORPORATION."

               (b) In addition to the foregoing legend, any certificate
representing any shares, other than shares which have been registered with the
Securities and Exchange Commission (the "Commission") pursuant to an effective
registration statement under the Act with respect to which no stop order
suspending the effectiveness thereof has been issued, shall have endorsed
thereon substantially the following legends:

               (i)    "THE SHARES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
                      REGISTERED UNDER THE SECURITIES ACT OF 1933v AS AMENDED
                      (THE "ACT") NOR UNDER ANY APPLICABLE STATE LAW, AND SUCH
                      SHARES MAY NOT BE SOLD, TRANSFERRED, ASSIGNED OR OTHERWISE
                      DISPOSED OF UNLESS A REGISTRATION STATEMENT UNDER THE ACT
                      WITH RESPECT TO SUCH DISPOSITION SHALL THEN BE IN EFFECT
                      AND ALL APPLICABLE STATE AND BLUE SKY LAWS HAVE BEEN
                      COMPLIED WITH, OR UNLESS THE PERSON REQUESTING THE
                      TRANSFER OF SUCH SHARES SHALL FURNISH AN OPINION OF
                      COUNSEL (BOTH COUNSEL AND OPINION TO BE SATISFACTORY TO
                      THE CORPORATION) TO THE EFFECT THAT SUCH SALE, TRANSFER,
                      ASSIGNMENT OR DISPOSITION WILL NOT INVOLVE ANY VIOLATION
                      OF THE ACT OR ANY SUPERSEDING STATUTE OR ANY APPLICABLE
                      STATE OR BLUE SKY LAWS."

               (ii)   Any legend required to be placed thereon by applicable
                      state securities laws.

        8. No Obligation to Transfer. The Company shall not be required (i) to
transfer or have transferred on its books any Shares which shall have been sold
or transferred in violation of any of the provisions set forth in this
Agreement, or (ii) to treat as the owner of such Shares or to accord the right
to vote as such owner or to pay dividends to any transferee to whom such Shares
shall have been so transferred.

<PAGE>   12

        9. Further Assurances. The parties agree to execute such further
instruments and to take such further action as may reasonably be necessary to
carry out the intent of this Agreement.

        10. Notices. Any notice required or permitted hereunder shall be given
in writing and shall be deemed effectively given upon personal delivery or upon
deposit in the United States Post Office, by registered or certified mail, with
postage prepaid, addressed to the other party hereto at the address shown below
his signature or at such other address as such party may designate from time to
time by advance written notice to the other party hereto.

        11. Governing Law. This Agreement shall be construed, and the provisions
hereof shall be enforced, in accordance with the laws of the State of Delaware.

        12. Assigns. This Agreement shall be binding upon and inure to the
benefit of the Company and its successors and assigns and, subject to the
restrictions set forth herein on Purchaser's transfer of the Shares, shall be
binding upon and Inure to the benefit of Purchaser, his heirs, executors,
administrators, guardians, transferees and assigns.

        13. Entire Agreement; Amendments. This Agreement constitutes the entire
agreement of the parties with respect to the subject matter hereof. This
Agreement may be amended, modified or supplemented only by a written agreement
signed by both of the parties hereto.

        14. Titles and Headings. The section titles and headings herein are for
convenience only and are not to be considered in construing or interpreting this
Agreement.

        15. Execution in Counterparts. This Agreement may be executed in any
number of counterparts, each of which shall be deemed for all purposes to be an
original and all of which together shall be deemed for all purposes to be one
agreement.

        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

                                        DALLAS SEMICONDUCTOR CORPORATION

Address for notices:
4350 Beltwood Parkway South
Dallas, Texas  75244

                                        By:
                                            ------------------------------------

                                        PURCHASER

                                        ----------------------------------------

                                        Address:
                                                 -------------------------------

                                        ----------------------------------------

<PAGE>   13

                                  AMENDMENT TO
                             SHAREHOLDER'S AGREEMENT

        THIS AMENDMENT is made as of the ____ day of ____________, 19__, by and
between DALLAS SEMICONDUCTOR CORPORATION, a Delaware corporation (the
"Company"), and ______________________________________________________________
(the "Purchaser").

        WHEREAS, the Company and Purchaser entered into that certain
Shareholder's Agreement ("Agreement") dated as of _________________, 19__.

        WHEREAS, on _________________, 19__, subsequent to the execution and
delivery of said Agreement, Purchaser was granted an additional option to
purchase up to _______ shares of the Company's Common Stock ("New Shares") under
the Company's 1987 Stock Option Plan, which are included within the definition
of "Additional Stock" as provided in Paragraph 5 of the Agreement;

        WHEREAS, Purchaser and the Company desire to alter the terms under the
Agreement as it relates to the New Shares;

        NOW, THEREFORE, IT IS HEREBY AGREED:

        1. Defined Terms. Terms used herein and not otherwise defined herein
shall have the same meanings as defined for such terms in the Agreement.

        2. Repurchase Right. The New Shares shall be subject to the Repurchase
Right as provided in Paragraph 2 of the Agreement, except that the terms thereof
(as they relate only to the New Shares, but to no other Shares) shall be amended
as follows:

               (a) For purposes of determining the Repurchase Right with respect
to the New Shares, the parties hereby acknowledge and agree that the
Commencement Date (only with respect to the New Shares) shall be deemed to be
______________, 19__.

               (b) The percentage of the New Shares which are subject to the
Repurchase Right shall be determined as follows:

<TABLE>
<CAPTION>
                  Length of Time Employee
                  Has Been Employed by the                  Percentage of
                     Company Since the                    Shares Subject to
                     Commencement Date                    Repurchase Right
                     -----------------                    ----------------
<S>                                                       <C>
               Less than 4 completed quarters                    100%
               4 completed quarters                               75%
               5 completed quarters                            68.75%
               6 completed quarters                            62.50%
               7 completed quarters                            56.25%
</TABLE>

<PAGE>   14

<TABLE>
<CAPTION>
                  Length of Time Employee
                  Has Been Employed by the                  Percentage of
                     Company Since the                    Shares Subject to
                     Commencement Date                    Repurchase Right
                     -----------------                    ----------------
<S>                                                       <C>
               8 completed quarters                               50%
               9 completed quarters                            43.75%
               10 completed quarters                           37.50%
               11 completed quarters                           31.25%
               12 completed quarters                              25%
               13 completed quarters                           18.75%
               14 completed quarters                           12.50%
               15 completed quarters                            6.25%
               16 or more completed quarters                     None
</TABLE>

        3. Agreement Ratified. Except as expressly amended hereby, the Agreement
is and shall remain in full force and effect and is hereby ratified and
confirmed in all respects.

        4. Entire Agreement. This Amendment, together with the Agreement,
constitute the entire agreement of the parties with respect to the subject
matter hereof. The Agreement may be further amended, modified and supplemented
only by a written agreement signed by both of the parties hereto.

        5. Titles and Headings. The section titles and headings herein are for
convenience only and are not to be considered in construing or interpreting this
Amendment or the Agreement.

        IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and year first above written.

                                        DALLAS SEMICONDUCTOR CORPORATION

                                        By:
                                            ------------------------------------

                                        PURCHASER:

                                        ----------------------------------------

                                        2

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