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                                                         Exhibit 10.19

                                                         [U.S. Bank Letterhead]




December 30, 1996


C. Albert Koob
Chief Financial Officer
Art Fletcher
Treasurer and Director of Financial Planning
SUMMIT DESIGN, INC. ("SUMMIT")
9305 S.W. Gemini Drive
Beaverton, OR  97005-7158

Dear Al and Art:

I am pleased to advise you that the United States National Bank of Oregon
("Bank") has approved the request of Summit Design, Inc. ("Summit"), to amend
the limit, terms and conditions of the existing $2,000,000 operating line of
credit, based upon the improved financial position of Summit.

Due to the number of changes, this correspondence will replace the May 22,
1996 commitment letter from US Bank to Summit which detailed the terms and
conditions of the line of credit.  A copy of the May 22, 1996 commitment
letter is attached for your convenience.

                            OPERATING LINE OF CREDIT

BORROWER:           Summit Design, Inc.

PURPOSE:            General Corporate Purposes.

BORROWING LIMIT:    $1,000,000.00 (Reduced from $2,000,000 at Summit's request.)

GUARANTORS:         None

EXPIRY:             April 30, 1997.  The Expiry date has been established to
                    review Summit's line of credit annually after receipt of the
                    year end financial statements.

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Summit Design, Inc.
1/15/97                       ACKNOWLEDGEMENT COPY
Page 2



RATE:     United States National Bank of Oregon Prime(1) rate plus a flexible
          percentage as determined quarterly, by the Borrower's debt to Tangible
          Net Worth level exhibited in the chart below.

          Debt to Tangible Net Worth is defined as (Total Liabilities - Unearned
          Revenue)/(Shareholders' Equity - Intangibles).


                                     Debt/Worth         Pricing

            GREATER THAN OR EQUAL TO    0.51            Prime + 0.75%
                                    .26 to .050         Prime + 0.50% *
               LESS THAN OR EQUAL TO    0.25            Prime +   0%

                       *    The last quarter ended September 30, 1996.  However,
                            Summit completed their IPO in October, 1996.  In
                            order to provide Summit the opportunity to price
                            this line with the benefit of the equity obtained
                            from the IPO, the initial rate will utilize the
                            October, 1996 financial results.  The debt to worth
                            ratio as of October 31, 1996 was .28:1.00. Going
                            forward, the rate will be adjusted quarterly
                            beginning with the 12-31-96 year end.

REPAYMENT TERMS:
          Interest shall be payable monthly on the 1st day of each month.
          Principal shall be payable on the earlier of April 30, 1997, or
          demand by the Bank.  Repayment of each advance received by Borrower
          under the line of credit is subject to the terms of the promissory
          note evidencing that advance, as well as all terms and conditions of
          this letter.  In the event of any conflict between the two, the terms
          and conditions of the promissory note shall control.

FEES:     UP-FRONT FEE:   Initial up-front fee of 1/4 of 1% of the amount of the
          line of credit, due upon acceptance ($5,000).  Note:  This was
          previously paid with the May, 1996 annual renewal.

          COMMITMENT FEE:   A 1/8 of 1% fee, annualized, on the unused portion
          of the line of credit, payable quarterly in arrears.  This is a
          reduction of the current commitment fee of 1/4% and will be effective
          January 1, 1997.




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  (1) The interest rate charged to Borrower is tied to the Prime Rate of
      United States National Bank of Oregon. Borrower is advised that Bank's
      Prime Rate is the rate of interest which the Bank from time to time
      identifies and publicly announces as its Prime Rate, and is not
      necessarily, for example, the lowest rate of interest which the Bank
      collects from any Borrower or group of borrowers.

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Summit Design, Inc.
1/15/97                       ACKNOWLEDGEMENT COPY
Page 3



COLLATERAL:    The revolving line of credit provides for a flexible
               collateral position according to the following matrix.  The
               assets of the Borrower which are referenced below include a
               first lien position in all accounts, contract rights, chattel
               paper, general intangibles and inventory.

QUICK RATIO*   COLLATERAL
GREATER THAN
    1.75:1.00  Unsecured with negative pledge agreement.

LESS THAN OR
EQUAL TO
    1.75:1.00  Unsecured with negative pledge, if not borrowing; but
               converts to secured if ratio falls below 1.75 benchmark
               for two consecutive quarters.  If borrowing and the ratio
               falls in this category, the line of credit will be secured.
LESS THAN OR
EQUAL TO
    1.25:1.00  Line is margined at 75% of eligible accounts receivable.

               *Quick ratio is defined as ((Cash + Net Trade Accounts) /
               (Current Liabilities - Current Portion of Unearned Revenue)).

DOCUMENTATION: Execution of Notes, Loan Agreements, Security Agreements,
               UCC Financing Statements and all other documentation required
               by the Bank in a form satisfactory to the Bank.

BORROWER WILL COMPLY WITH THE FOLLOWING QUARTERLY FINANCIAL COVENANTS:

               1.   The CURRENT RATIO will no longer be a covenant.

               2.   TANGIBLE NET WORTH shall not be less than $7,500,000 plus
                    80% of net new equity raised from sources outside of normal
                    operations.  Tangible Net Worth is defined as
                    (Equity - Intangibles).  Note: Intangibles include all
                    capitalized software.

               3.   TOTAL LIABILITIES TO TANGIBLE NET WORTH shall not exceed .75
                    to 1.00. Total Liabilities to Tangible Net Worth is defined
                    as (Total Liabilities minus Deferred Revenue)/(Tangible Net
                    Worth).

               4.   MAXIMUM LOSS.  Net losses over the prior four quarters shall
                    not exceed $5,000,000.00.

               Failure to maintain these covenants will be considered an event
               of default under the loan documents.


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Summit Design, Inc.
1/15/97                       ACKNOWLEDGEMENT COPY
Page 4

OTHER TERMS AND CONDITIONS:

          1.   Distribution in the form of dividends shall not exceed 25% of net
               income, measured annually as of December 31.

REPORTING REQUIREMENTS:
          -    Quarterly financial statements to be submitted within 45 days of
               quarter end.
          -    Annual CPA audited financial statements to be submitted within 90
               days of fiscal year end.
          -    If the Quick Ratio falls to 1.25:1.00 or below:  A Borrower's
               Certificate will be submitted with each advance, and a Borrower's
               Certificate will accompany the monthly AR and AP agings.

ADVANCE STRUCTURE:
               Advances will be limited to the Borrowing Limit when the Quick
               Ratio is greater than 1.25 : 1.00.  When the quick ratio is less
               than or equal to 1.25 : 1.00, advances will be limited to 75% of
               eligible accounts receivable to 120 days after the date of
               invoice.

               Disbursements under the line of credit shall terminate on the
               earlier occurrence of the date indicated above as the Expiry Date
               or the date on which this Bank, in its sole discretion,
               determines that there has been a material adverse change in the
               financial condition or management of the Borrower, or determines
               that there has been any non-compliance with any term or condition
               stated herein.  Non-compliance within the conditions and terms of
               this letter and all other loan documents will be considered as an
               event of default, entitling the Bank to all the default
               provisions as provided for in documents evidencing this line of
               credit.

OTHER:         Under Oregon law, most agreements, promises and commitments made
               by lenders after October 3, 1989, concerning loans and other
               credit extensions which are not for personal, family or household
               purposes or secured solely by the borrower's residence must be in
               writing, express consideration and be signed by the lender to be
               enforceable.

If the above terms and conditions to extend this credit facility to
Summit Design, Inc. are acceptable to you, please sign and return the
acknowledgment copy of this letter on or before January 15, 1997.

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Summit Design, Inc.
1/15/97                       ACKNOWLEDGEMENT COPY
Page 5

We are pleased to provide you this borrowing accommodation and look forward to
serving your banking needs in the future.

Sincerely,


/s/ Jeff A. Killian

Jeff A. Killian
Vice President

THE UNDERSIGNED HEREBY ACKNOWLEDGES AND ACCEPTS THIS OFFER TO EXTEND CREDIT
SUBJECT TO THE TERMS AND CONDITIONS STATED ABOVE.

SUMMIT DESIGN, INC.

BY:  /s/ C. Albert Koob       CFO                         12/31/96
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