[PARPORT] Speed in EPP Mode Input

From: Wolfgang Mes (wolfgang@wmsickte.escape.de)
Date: Sun Mar 25 2001 - 04:33:35 EST

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    Hi,

    I am trying to build a hardware which is attached to an EPP Printer Port
    and doing reading and writing. I have obtained the following behaviour:

    - at the start of the Input cycle, DATASTB is low for 300ns. 150ns of
       this time may be related to the device.
    - if I do word or doubleword IO, DATASTB is high for 400ns between
       the cycles. 50ns of this time may be related to the device.
    - After execution of the IO instruction (1,2,or 4 bytes), DATASTB is
       high for 2 us.

    So, if I use 4-byte-IO, I will get 4x300+3x400+1x2000 = 4400ns
    = 1.1 us/Byte as maximum transfer speed.

    These tests run on a AMD Atlon 700 MHz System (don't know the chip
    set, may be from AMD).

    So, obviously, the speed of the IO is bounded to the PC chip set,
    and this will limit the IO bandwith far below the actual speed of the
    connected device.

    Is this behaviour common? Is this a typical speed for EPP inputs?

    best regards

    Wolfgang

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