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EPP Test: Determining Your Computer's Parallel Port Type

This document steps through a brief test that allows the user to ascertain whether or not their computer is using an Enhanced or Centronics parallel port. Note that Debug, the program used here, is not case or space sensitive.

1. Type Debug at the C:\ prompt. A "-" should appear.

2. Type "d 40:8 L2" and hit RETURN. One line should be printed that has numbers on the left, in the middle and on the right. The two numbers in the middle represent the hex address of your parallel port. If the number is 78 03 then your parallel port is at address 0378. It could be at 3BC, 3CA or any other address.

3. Add 2 to this address: 378 becomes 37A. Type "i 37A" and press RETURN. This is inputting data from bit 5 of the parallel port. You will get something like EC back. Bit 5 is as follows:

Bit 7 6 5 4 3 2 1 0 Code E C Code 1 1 1 0 1 1 0 0

4. The idea is to set bit 5 to a 1 without disturbing the other bits. If your parallel port is an EPP, then setting bit 5 to 1 causes the port to become an input port. Whether or not bit 5 is set to a 1, type "o 37A EC" and RETURN followed by "i 37A" RETURN, which should return EC. This sets this address to EC and then reads it back to make sure that it was in fact set correctly.

5. Type "o 378 CA" RETURN. CA is a random number that is output to the parallel port. If your address was different to 378 then use that address instead of 378.

6. Type "i 378" RETURN . This reads back information from the parallel port. What is returned indicates the type of port that you have. If CA is returned then you have a normal, Centronics parallel port. If you get different figures back then you have an EPP.

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