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                                                                   EXHIBIT 10.13


                                 PROMISSORY NOTE



$1,250,000                                                       August 21, 1997
                                                           San Diego, California

        For value received, the undersigned (collectively "Payor") promises to
pay to FALCON SYSTEMS, INC. ("FALCON"), a California corporation, or order
("Holder"), in lawful money of the United States of America and in immediately
available funds, the principal sum of one million two hundred fifty thousand
dollars ($1,250,000) (the "Principal Amount") together with interest thereon at
the times and in the manner set forth below.

        This note (the "Note") is executed and delivered as part of the Purchase
Price pursuant to that certain Asset Purchase Agreement of even date herewith
among Payor, Holder and the sole shareholder of Holder (the "Purchase
Agreement"). Notwithstanding any other provision of this Note, this Note shall
be subject in all respects to the provisions of that certain Indemnity Agreement
of even date herewith among Payor, Founding Partners, a California general
partnership (the "Partnership"), each Partner of the Partnership, Falcon and
Craig Caudill (the "Indemnity Agreement"), including but not limited to Section
1(d), 1(e) and 2 of the Indemnity Agreement.

        1. REPAYMENT OF PRINCIPAL AND INTEREST. Subject to the terms of this
Note, the outstanding Principal Amount shall be repaid, together with accrued
interest thereon as provided below, in equal monthly combined principal and
interest payment of twenty-six thousand five hundred fifty eight dollars and
eighty-one cents $26,558.81, with the first payment due on the date that is one
(1) month from the date hereof and subsequent payments due each monthly
anniversary thereafter for a period of five years following the date hereof.

        2. INTEREST RATE. Subject to the terms of this Note, Payor promises to
pay interest on the outstanding principal amount hereof from the date hereof
until payment in full in accordance with paragraph 1, which interest shall be
payable at the rate of ten percent (10%) per annum or the maximum rate
permissible by law (which under the laws of California shall be deemed to be the
laws relating to permissible rates of interest on commercial loans), whichever
is less.

        3. DEFAULT RATE. If the undersigned fails to pay any of the principal or
accrued interest when due, then all unpaid amounts, including all accrued but
unpaid interest, shall bear interest at 18% per annum, or the maximum rate
permissible by law in the event of a default of a promissory note of this type
and nature, whichever is less.


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        4. PLACE OF PAYMENT. Payments on this Note shall be payable at Holder's
office located at 485 Crocker Road, Sacramento, California 95864, unless another
place of payment shall be specified in writing by Holder.

        5. SECURITY. This note is subject to the security and subordination
provisions of that certain Security Agreement by and between Artecon, Inc., a
California corporation, and Holder of even date herewith (the "Security
Agreement"), as well as the security provisions of that certain Subordination
Agreement by and among Payor and Holder of as of the date hereof.

        6. APPLICATION OF PAYMENTS. Payments on this Note shall be applied first
to accrued interest, and thereafter to the outstanding principal balance
thereof.

        7. PREPAYMENTS. This Note may be prepaid in whole or in part at any time
without premium or penalty.

        8. MISCELLANEOUS.

               (a) This Note will be considered in default if, after fifteen
(15) days following written notice to Payor of Payor's failure to make any
payment of principal or accrued interest hereunder, such failure remains uncured
(provided that such notice shall not be required more than three times in any
calendar year). In such event, at Holder's option, all outstanding principal and
accrued interest and any other amounts payable under this Note will become due
and payable.

               (b) Except as otherwise provided in this Note, Payor, all
endorsers, guarantors and sureties of this Note, and each of them, and their
successors and assigns, hereby waive demand, presentment for payment, notice of
non-payment, protest and notice of protest, and notice of dishonor, and
expressly agree that without notice, this Note or any payment due date hereunder
may be extended from time to time, and consent to acceptance of additional or
substitute parties or both, or the release of any party liable with respect to
this Note, all without affecting in any way their liability.

               (c) If Payor fails to make any interest or installment payment
when due, Payor promises to pay all costs and expenses of collection and
reasonable attorneys' fees incurred by Holder to enforce the terms of this Note
and/or the Security Agreement including, without limitation, those expenses and
fees which may be incurred in connection with the appointment of a receiver and
all appearances in bankruptcy or insolvency proceedings. In any action brought
under or arising out of this Note, Payor hereby consents to the jurisdiction of
any competent court within the State of California and to service of process by
any means authorized by California law.


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               (d) Holder shall, at all times, have the right to proceed against
any portion of the security for this Note in such order and in such manner as
Holder may consider appropriate without waiving any rights with respect to any
such security. Any delay or omission on the part of Holder in exercising any
right hereunder shall not operate as a waiver of such right, or any other right
under this Note.

               (e) This Note may not be terminated or amended orally, but only
by a termination or amendment in writing signed by Holder.

               (f) Governing Law. This Note shall be governed by, and construed
and entered in accordance with, the laws of the State of California, as applied
to contracts entered into by California residents within the State of
California, which contracts are to be performed entirely within the State of
California.

               (g) The provisions of this Note shall inure to the benefit of and
be binding on any successor to Payor and shall extend to any holder hereof.

                                  ARTECON, INC.


                                  By: /s/ James L. Lambert
                                     -------------------------------
                                     James L. Lambert, President


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