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                                                                   EXHIBIT 10.21

      THE SECURED CONVERTIBLE PROMISSORY NOTE EVIDENCED OR CONSTITUTED HEREBY,
AND ALL SHARES OF COMMON STOCK ISSUABLE HEREUNDER, HAVE BEEN AND WILL BE ISSUED
WITHOUT REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "1933
ACT") AND MAY NOT BE SOLD, OFFERED FOR SALE, TRANSFERRED, PLEDGED OR
HYPOTHECATED WITHOUT REGISTRATION UNDER THE ACT UNLESS EITHER (i) MAKER HAS
RECEIVED AN OPINION OF COUNSEL, IN FORM AND SUBSTANCE REASONABLY SATISFACTORY TO
MAKER, TO THE EFFECT THAT REGISTRATION IS NOT REQUIRED IN CONNECTION WITH SUCH
DISPOSITION OR (ii) THE SALE OF SUCH SECURITIES IS MADE PURSUANT TO SECURITIES
AND EXCHANGE COMMISSION RULE 144.

                       SECURED CONVERTIBLE PROMISSORY NOTE

$3,150,000                                                    September 30, 1999

      FOR VALUE RECEIVED, the undersigned, GENERAL AUTOMATION, INC., a Delaware
corporation ("Maker"), promises to pay to the order of PACIFIC MEZZANINE FUND,
L.P., a California limited partnership ("Payee", Payee and any subsequent
holder(s) hereof are hereinafter referred to collectively as "Holder"), at the
office of Payee at 2200 Powell Street, Suite 1250, Emeryville, California 94608,
or at such other place as Holder may designate to Maker in writing from time to
time, the principal sum of THREE MILLION, ONE HUNDRED FIFTY THOUSAND DOLLARS
($3,150,000), together with interest on the outstanding principal balance hereof
from the date hereof at the Base Rate (as such term is defined in the Loan
Agreement by and between Maker and Payee of even date herewith (the "Loan
Agreement")). All interest hereunder shall be calculated based on a 360-day year
and paid for the actual number of days elapsed.

      Interest only on the outstanding principal balance hereof shall be due and
payable monthly, in arrears, with the first installment being payable on the
first (1st) day of November, 1999, and subsequent installments being payable on
the first (1st) day of each succeeding month thereafter until the Maturity Date
(as such term is defined in the Loan Agreement), at which time the entire
outstanding principal balance, together with all accrued and unpaid interest,
shall be immediately due and payable in full.

      The indebtedness evidenced hereby may be prepaid in whole or in part, at
any time and from time to time, without penalty, subject to the terms of the
Loan Agreement. Any such prepayments shall be credited first to any accrued and
unpaid interest and then to the outstanding principal balance hereof.

      This Note will be a fully-registered note on the books of Maker and will
be issued only in fully-registered form. Maker will cause to be kept at its
principal office a register for the registration and transfer of the Notes. The
name and address of each Holder hereof, the transfer thereof and the names and
addresses of any transferee hereof, or any interest therein, shall be recorded
in such register. Until a transfer hereof is duly registered on the books of
Maker, Maker


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may treat the registered Holder thereof as the owner for all purposes. This Note
is subject to the restrictions on transfer set forth herein and in the Loan
Agreement.

      Time is of the essence of this Note. It is hereby expressly agreed that in
the event that any default be made in the payment of principal or interest as
stipulated above, which default is not cured following the giving of any
applicable notice and within five (5) business days; or in the event that any
default or event of default shall occur under the Loan Agreement, which default
or event of default is not cured following the giving of any applicable notice
and within any applicable cure period set forth in said Loan Agreement; or
should any default by Maker be made in the performance or observance of any
covenants or conditions contained in any other instrument or document now or
hereafter evidencing, securing or otherwise relating to the indebtedness
evidenced hereby (subject to any applicable notice and cure period provisions
that may be set forth therein); then, and in such event, the entire outstanding
principal balance of the indebtedness evidenced hereby, together with any other
sums advanced hereunder, under the loan agreement and/or under any other
instrument or document now or hereafter evidencing, securing or in any way
relating to the indebtedness evidenced hereby, together with all unpaid interest
accrued thereon, shall, at the option of Holder and without notice to Maker, at
once become due and payable and may be collected forthwith, regardless of the
stipulated date of maturity. Upon the occurrence of any default as set forth
herein, at the option of Holder and without notice to Maker, all accrued and
unpaid interest, if any, shall be added to the outstanding principal balance
hereof, and the entire outstanding principal balance, as so adjusted, shall bear
interest thereafter until paid at the Default Rate (as such term is defined in
the Loan Agreement), regardless of whether or not there has been an acceleration
of the payment of principal as set forth herein. All such interest shall be paid
at the time of and as a condition precedent to the curing of any such default.

      In the event this Note is placed in the hands of an attorney for
collection, or if Holder incurs any costs incident to the collection of the
indebtedness evidenced hereby, Maker and any indorsers hereof agree to pay to
Holder an amount equal to all such costs, including without limitation all
actual reasonable attorney's fees and all court costs.

      Presentment for payment, demand, protest and notice of demand, protest and
nonpayment are hereby waived by Maker and all other parties hereto. No failure
to accelerate the indebtedness evidenced hereby by reason of default hereunder,
acceptance of a past-due installment or other indulgences granted from time to
time, shall be construed as a novation of this Note or as a waiver of such right
of acceleration or of the right of Holder thereafter to insist upon strict
compliance with the terms of this Note or to prevent the exercise of such right
of acceleration or any other right granted hereunder or by applicable laws. No
extension of the time for payment of the indebtedness evidenced hereby or any
installment due hereunder, made by agreement with any person now or hereafter
liable for payment of the indebtedness evidenced hereby, shall operate to
release, discharge, modify, change or affect the original liability of Maker
hereunder or that of any other person now or hereafter liable for payment of the
indebtedness evidenced hereby, either in whole or in part, unless Holder agrees
otherwise in writing. This Note may not be changed orally, but only by an
agreement in writing signed by the party against whom enforcement of any waiver,
change, modification or discharge is sought.



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      The indebtedness and other obligations evidenced by this Note are further
evidenced by (i) the Loan Agreement and (ii) certain other instruments and
documents, as may be required to protect and preserve the rights of Maker and
Payee as more specifically described in the Loan Agreement.

      Payment of this Note is secured by a security interest in all assets of
Maker pursuant to a Security Agreement, a Pledge Agreement, a Patent and
Trademark Security Agreement and Copyright Security Agreement, each dated as of
the date hereof (collectively, the "Security Agreements").

      All or any portion of this Note, including accrued interest, is
convertible at the option of the Holder at any time prior to the Maturity Date
into shares of Maker's Common Stock ("Conversion Stock") at the Conversion Rate
(as such term is defined in the Loan Agreement) and shall also automatically
convert at the Conversion Rate under certain circumstances more particularly
described in the Loan Agreement. The Holder of this Note shall give Maker five
(5) business days' written notice of his election to convert setting forth the
name and address of such Holder and the amount of the principal and accrued
interest of the Note to be converted. Holder shall tender this Note to Maker
together with such election. Maker shall deliver the shares issuable upon
conversion hereof within fifteen (15) business days after receipt of such
conversion notice. If less than all of this Note is converted in shares of
stock, Maker shall issue to Holder a new note for the remaining principal amount
together with an acknowledgment of the remaining accrued interest hereon.

      The Holder, by acceptance hereof, agrees that, absent an effective
registration statement filed with the SEC under the 1933 Act, covering the
disposition or sale of this Note or the Conversion Stock issued or issuable upon
conversion hereof, as the case may be, and registration or qualification under
applicable state securities laws, such Holder will not sell, transfer, pledge,
or hypothecate any or all such Note or Conversion Stock, as the case may be,
unless either (i) Maker has received an opinion of counsel, in form and
substance reasonably satisfactory to Maker, to the effect that such registration
is not required in connection with such disposition or (ii) the sale of such
securities is made pursuant to SEC Rule 144.

      By acceptance of this Note, the Holder hereby represents, warrants and
covenants that any shares of stock purchased upon conversion of this Note shall
be acquired for investment only and not with a view to, or for sale in
connection with, any distribution thereof; that the Holder has had such
opportunity as such Holder has deemed adequate to obtain from representatives of
Maker such information as is necessary to permit the Holder to evaluate the
merits and risks of its investment in Maker; that the Holder is able to bear the
economic risk of holding such shares as may be acquired pursuant to the
conversion of this Note for an indefinite period; that the Holder understands
that the shares of stock acquired pursuant to conversion of this Note will not
be registered under the 1933 Act (unless otherwise required pursuant to exercise
by the Holder of the registration rights granted to the Holder) and will be
"restricted securities" within the meaning of Rule 144 under the 1933 Act and
that the exemption from registration under Rule 144 will not be available for at
least one year from the date of conversion of this Note, and even then will not
be available unless a public market then exists for the stock, adequate
information concerning Maker is then available to the public, and other terms
and conditions of Rule 144 are



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complied with; and that all stock certificates representing shares of stock
issued to the Holder upon conversion of this Note may have affixed thereto a
legend substantially in the following form:

            THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
            SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR UNDER THE
            SECURITIES LAWS OF ANY STATE. THESE SECURITIES ARE SUBJECT TO
            RESTRICTIONS ON TRANSFERABILITY AND RESALE AND MAY NOT BE
            TRANSFERRED OR RESOLD EXCEPT AS PERMITTED UNDER THE ACT AND THE
            APPLICABLE STATE SECURITIES LAWS, PURSUANT TO REGISTRATION OR
            EXEMPTION THEREFROM. INVESTORS SHOULD BE AWARE THAT THEY MAY BE
            REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS INVESTMENT FOR AN
            INDEFINITE PERIOD OF TIME. THE ISSUER OF THESE SECURITIES MAY
            REQUIRE AN OPINION OF COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO
            THE ISSUER TO THE EFFECT THAT ANY PROPOSED TRANSFER OR RESALE IS IN
            COMPLIANCE WITH THE ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

      All shares of common stock issuable upon conversion of this Note shall be
"Registrable Securities" or such other definition of securities entitled to
registration rights pursuant to the Investors' Rights Agreement dated September
30, 1999, by and among the Maker and the original Payee hereof.

      Subject to and under the circumstances set forth in the Loan Agreement,
Payee has agreed to subordinate its rights under the Loan Agreement, this Note
and the Loan Documents (as such term is defined in the Loan Agreement) to
certain senior debt, capital lease and similar obligations.

      All agreements herein made are expressly limited so that in no event
whatsoever, whether by reason of advancement of proceeds hereof, acceleration of
maturity of the unpaid balance hereof or otherwise, shall the amount paid or
agreed to be paid to Holder for the use of the money advanced or to be advanced
hereunder exceed the maximum rate of interest allowed by law (the "Maximum
Rate"). If, from any circumstances whatsoever, the fulfillment of any provision
of this Note or any other agreement or instrument now or hereafter evidencing,
securing or in any way relating to the indebtedness evidenced hereby shall
involve the payment of interest in excess of the Maximum Rate, then, ipso facto
the obligation to pay interest hereunder shall be reduced to the Maximum Rate;
and if from any circumstance whatsoever, Holder shall ever receive interest, the
amount of which would exceed the amount collectible at the Maximum Rate, such
amount as would be excessive interest shall be applied to the reduction of the
principal balance remaining unpaid hereunder and not to the payment of interest.
This provision shall control every other provision in any and all other
agreements and instruments



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existing or hereafter arising between Maker and Holder with respect to the
indebtedness evidenced hereby:

      This Note is tended as a contract under and shall be construed and
enforceable in accordance with the laws of the State of California, except to
the extent that federal law may be applicable to the determination of the
Maximum Rate.

                                         MAKER:

                                         GENERAL AUTOMATION, INC.,
                                         a Delaware corporation

                                         By:
                                         -----------------------------------
                                         Title:


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