
			  E15/E17 SIGNATURE MODE PROBLEM:


    Many modern EPROM devices include a recent feature that allows them
    to be electronically identified.  This is true of an actual 27C64
    EPROM, but unfortunately, the TMS320E1x devices do not support this
    feature.

    On an actual 27C64, the identification of the manufacturer and type of
    device is made by reading a bit pattern in the EPROM cell.	This read
    is accomplished by putting a relatively high voltage (13.5v) on the
    A9 address line.  Since the TMS320E1x devices are not designed to
    support the signature mode, this high voltage can (and usually does)
    damage the device.

    Many newer model prom-programmers also support this feature in their
    read and program algorithms.  Some examples of those that do are:
    DATA I/O Unisite 40 and System 29B.  Both of these machines default
    with the signature mode enabled after power-up.  Therefore, these
    modes must be disabled, and can be disabled by entering SELECT CODE
    BC.  This must be done upon each power-up of the unit in order to
    protect the device.

    As further protection, and to elimate having to manually disable this
    function on prom-programmers, a simple work-around was developed.
    If a 3.9k resistor is placed in series with address line A9 (that is,
    between pin 29 of the TMS320E1x and pin 24 of the EPROM pinout),
    the device will be protected from the high voltage, and still retain
    its full functionality.  This protection is designed in to Texas
    Instruments programming adapter (p/n: RTC/PGM320A-06) sold after
    September, 1988.  Earlier versions of the adapter must be upgraded
    either by the user or by Texas Instruments factory repair.

    Please note that this resistor enhancement does NOT appear in the
    programmer schematic shown in Appendix G of the TMS320C1X Users Guide.
    If a customer is building his own adapter, it must be included.

    To upgrade early version of the TI adapter, use the following procedure:

    TO UPGRADE THE 40-PIN DIP ADAPTOR (RTC/PGM320A-06) CUT THE TRACE ON	THE
    SOLDER SIDE	THAT RUNS BETWEEN PIN 29 OF THE	40-PIN ZIF SOCKET AND PIN
    24 OF THE 28-PIN ADAPTOR (GOLD LEGS).  SOLDER A 3.9K 1/4W RESISTOR
    BETWEEN THE	TWO POINTS (ONE	END TO THE SOLDER JOINT	OF PIN 29 ON
    THE	ZIF SOCKET AND THE OTHER END TO	THE GOLD LEG OF	PIN 24).

    TO UPGRADE THE 44-PIN CLCC ADAPTOR (RTC/PGM320C-06)	CUT THE	TRACE ON
    THE	SOLDER SIDE THAT RUNS BETWEEN PIN 24 OF	THE 28-PIN ADAPTOR (GOLD
    LEGS) AND THE FEEDTHRU THAT	IS APPROXIMATELY 1/16 INCH OUTSIDE THE
    DIP	FOOTPRINT.  SOLDER A 3.9K 1/4W RESISTOR	BETWEEN	THE TWO	POINTS
    (ONE END TO	THE GOLD LEG OF	PIN 24 AND THE OTHER LEG TO THE	FEEDTHRU).

    THE	USER CAN IDENTIFY WHETHER THEIR	EPROM ADAPTOR SOCKET NEEDS TO
    BE UPDATED BY LOOKING FOR A	GREEN DOT WITH THE LETTER "A" ON IT.
    THIS DOT ON	THE ADAPTOR SOCKET SIGNIFIES REVISION A.  REVISION A
    OF THE ADAPTOR SOCKET HAS BEEN UPGRADED AND	DOES NOT NEED TO BE
    MODIFIED WITH THE 3.9K OHM RESISTOR.  ADAPTOR SOCKETS BEFORE REVISION
    A (WITHOUT GREEN DOTS) SHOULD BE MODIFIED IMMEDIATELY.


   REH - 04/89
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