APPENDIX B- THE PROGRAM METHOD WORD


        The program method word tells PROMOS how you want the
    programming done. You have some latitude. If you check the
    TABLE of RECOMMENDED CONTROL and PROGRAM METHOD WORDS inside
    the back cover, you'll see a 'standard method' and three
    'intelligent' methods. We examine these in greater detail
    here.

    STANDARD PROGRAMMING

        In standard programming, the programming pulse applied to
    the EPROM is of constant duration, usually about 50 ms
    (milliseconds). This is always a time-consuming method. A
    2764 takes about 7 minutes to program this way. For PHW's
    from 0 to 3, PROMOS uses Pulse durations as follows:

             PMW                     PULSE DURATION

               0                          6 ms.
               1                         12 ms.
               2                         24 ms.
               3                         48 ms.

    INTELLIGENT METHODS FOR PROGRAMMING

        Intelligent methods for programming EPROM's have been
    developed which can greatly reduce the time required. These
    methods in effect 'test' the EPROM as the process goes on.
    It works like this: The address and data are set up and a
    short duration pulse Is applied. The EPROM is then read back
    and the data is compared. If the data doesn't 'verify', then
    another pulse is applied and so on. Programming time is
    accumulated. At some point the data 'sticks' and a positive
    verification is obtained.
       At this point, another longer 'margin' pulse is applied
    which is proportional in duration to the sum of the
    preceeding pulses. The data is verified once again, and the
    programmer then moves on to the next location.

       Intelligent #1- Developed by Jason-Ranheim, this method
    has been widely copied. It is the fastest way to program an
    EPROM. Programming starts with a short .1 ms pulse which
    doubles in duration with each failure to verify. The margin
    pulse is equal in length to the sum of all preceding pulses.

       Intelligent #2- In this method, short pulses of equal
    duration are applied. The margin pulse is 3 times the total
    accumulated pulse time. If after 25 ms of short pulses, a


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