
C ONTR OL S YS TE MS
J224 PCO24
2192-10479-000-000
Page 5
I/O map
The value written to the pointer register is used to select the on-board I/O location to be
accessed. This board occupies two consecutive addresses and has three I/O function registers
and three special registers.
Address
Read/Write
Write only
Read/Write
Register Name
Pointer register
Data Register
Register Function
On-board register
Data
to
from/to register
Base (180)
Base+1 (181)
read/write
I/O Function Registers
Pointer value
00
01
02
03
01
02
Register name
Read/Write
Write
Write
Write
Read
Read
Read
Register description
Group 0 outputs
Group 1 outputs
Group 2 outputs
Group 0 output latch state
Group 1 output latch state
Group 2 output latch state
G0
G1
G2
G0
G1
G2
Special Function Registers
The green User LED is controlled by bit 0 when the pointer register is loaded with 80h. The
board identification register can be used to confirm the board is present in the system and is
the correct board type. Other Pcbus I/O boards in Arcom’s range will return a different value.
Pointer value
80
Register name
User LED
Read/Write
Write
Comments
Writing 01 switches the green
LED on. Writing 00 switches it
off
Reading this register gives the
value 04
Writing 01 enables the outputs
Writing 00 disables the outputs
81
Board ident
Read
90
Output enable
Write
Address Switches
Sets the base address for the board in Pcbus I/O space.
Switch setting
SW2
8
Resulting Hexadecimal Base Address
SW1
1
SW3
0
180