Measurement-computing PC104-DO48H Instrukcja Użytkownika Pobierz pdf (Strona 11)

5.0 CONTROL & DATA REGISTERS

Each PC104-DO48 is composed of parallel output chips. Each address contains one

latch and one buffer controlling eight output pins. The ports are arranged in sets of

three, with an intervening NA (not used) address. This scheme allows compatibility

with software written to control 82C55 based boards when the 82C55 is used as all

outputs. On those boards every fourth address contains a control register.

The first address, or BASE ADDRESS, is determined by setting a bank of switches on

the board.

To write a control data to an output register, the individual bits must be set to 0 or 1

then combined to form a Byte.

The registers and their function are listed on the following table.

NoneNoneBASE + 3, 7

Port C OutputNoneBASE + 2, 6

Port B OutputNoneBASE + 1, 5

Port A OutputNoneBASE + 0, 4

WRITE FUNCTIONREAD FUNCTIONADDRESS

There are two sets of digital output lines. Each set has 24 outputs that are divided into

three ports of eight lines each. An 8-bit register accesses each port. The register

addresses are given in the table above and the bit maps below.

PORT A DATA

BASE ADDRESS + 0, 4

A0A1A2A3A4A5A6A7

01234567

PORT B DATA

BASE ADDRESS + 1, 5

B0B1B2B3B4B5B6B7

01234567

PORT C DATA

BASE ADDRESS + 2, 6

C0C1C2C3C4C5C6C7

01234567

1 2 ... 6 7 8 9 10 11 12 13 14 15 16

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Measurement-computing PC104-DO48H Instrukcja Użytkownika Strona 11