C-2
Register Maps
The I/O map and functions of the four addresses are shown in Table C-1.
All ports are 8-bits (1-byte) wide and require byte-oriented, read/write
operations rather than word (16-bit) operations.
Relay Output Register Data Format
Data are written to all eight relays as a single byte. Each of the eight bits
within a byte controls a single relay. A high bit (equal to 1) energizes
(closes the contacts of) a relay while a low bit (equal to 0) turns the relay
off.
This register is read to determine the state of the relays. A high bit
indicates that a relay is energized while a low bit indicates that the relay is
off.
Relay Output register bits are assigned as shown in Table C-2.
For example, to energize the relay controlling OP4 of a PDISO-8 board at
a base address of 300h, 00010000 binary (10h) is written to I/O address
300h.
Table C-1. I/O Map and Functions
I/O Address
Function
Read/Write
Base a0h
Relay outputs
R/W
Base a1h
Isolated control inputs
R
Base a2h
Not used
—
Base a3h
Not used
—
Table C-2. Relay Addresses in the Relay Output Register
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Base A0h
OP7
OP6
OP5
OP4
OP3
OP2
OP1
OP0
