Measurement-computing PC104-DIO48 Bedienungsanleitung PDF herunterladen (Seite 10)

3 CONTROL & DATA REGISTERS

We recommend that you use the Universal Library for all high level

programming. The following is basic information on the 82C55 control

and data registers and a table of control bytes for MODE 0 only. To

learn more about the other 82C55 modes, you will need the component

data book available from the component manufacturer.

Each PC104-DIO48 has two 82C55 parallel I/O chips. Each chip

contains three data and one control register occupying four consecutive

I/O address locations. The number of I/O locations occupied by a

PC104-DIO48 board is equal to 4 times the number of 82C55 chips on

the board or eight total.

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

of switches on the board.

The register descriptions follow all follow the format:

A0A1A2A3A4A5A6A7

01234567

The numbers along the top row are the bit positions within the 8-bit byte

and the numbers and symbols in the bottom row are the functions

associated with each bit.

To write to or read from a register in decimal or HEX, the bit weights in

Table 2-1 apply:

Table 3-1. Bit Weights

801287

40646

20325

10164

883

442

221

110

HEX VALUEDECIMAL VALUEBIT POSITION

To write a control word or data to a register, the individual bits must be

set to 0 or 1 then combined to form a byte. Data read from registers

must be analyzed to determine which bits are on or off.

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 23 24

Keine Kommentare

Measurement-computing PC104-DIO48 Bedienungsanleitung Seite 10