Chapter 10:
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. Figure 10–1 shows typical
I/O configurations. The digital I/O ports have the following specifications:
Each 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 10–1 Digital I/O connectors: J6 and J13 (arranged by function)
J6 – Digital I/O 1, J13 – Digital I/O 2
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
74
