Chapter 9: Bit-programmable digital I/O
Description
The bit-programmable digital I/O lines can be used to sense switch closures, turn
on lamps and LEDs, and interface with other devices that have TTL input or
output such as printers and scales. The digital I/O lines drive the Octagon MPB
series opto-isolation module racks directly, controlling AC and DC loads to 240V at
3A. Tables 9–1 and 9–2 show the pinout for the digital I/O connector, arranged by
function and by pin number. Figure 9–1 shows typical I/O configurations.
The I/O lines have the following specifications:
The I/O chip has 24 I/O lines, grouped into 3 ports of 8 bits
Each bit is programmable as either 5V input or 5V output
Read back state of each pin
Easy-to-program
Each line can sink and source 15 mA
Table 9–1
J9 arranged by function – digital I/O connector
J9 Digital I/O
Pin #
Port A
Pin #
Port B
Pin #
Port C
19
Bit 0
10
Bit 0
13
Bit 0
21
Bit 1
8
Bit 1
16
Bit 1
23
Bit 2
4
Bit 2
15
Bit 2
25
Bit 3
6
Bit 3
17
Bit 3
24
Bit 4
1
Bit 4
14
Bit 4
22
Bit 5
3
Bit 5
11
Bit 5
20
Bit 6
5
Bit 6
12
Bit 6
18
Bit 7
7
Bit 7
9
Bit 7
2
+5V
safe*
26
Gnd
* +5V safe is fused through a 750 mA automatic, resetting fuse
Note
See the Accessories appendix for connector information for the digital I/O
connector.
59
