Creating two sub-categories, Table 9 - 2 sub-categories / 8 states – CTI Products IOB I/O Interface User Manual
Page 16
IOB Hardware Reference
Theory of Operation
CTI Products, Inc.
68-11168-105
11
Creating Two Sub-categories
To create two sub-categories, one I/O bit must be reserved for the sub-category
selector. In Table 9, I/O bit 4 has been reserved for the sub-category selector.
You can see from the table that there are eight possible status messages that can
be defined for each sub-category. Because I/O bit 4 has been reserved as the
selector, all IOB pins that correspond to I/O bit 4 cannot be used by application
circuitry.
Input Value
Field
Sub-
category
#
Sub-category
Selector I/O
Bit
4
I/O Bit
Combinations
3 2 1
00
1
0
0 0 0
01
1
0
0 0 1
04
1
0
0 1 0
05
1
0
0 1 1
10
1
0
1 0 0
11
1
0
1 0 1
14
1
0
1 1 0
15
1
0
1 1 1
40
2
1
0 0 0
41
2
1
0 0 1
44
2
1
0 1 0
45
2
1
0 1 1
50
2
1
1 0 0
51
2
1
1 0 1
54
2
1
1 1 0
55
2
1
1 1 1
Table 9 - 2 Sub-categories / 8 States
Note: In this table, any I/O bit shown as a 0 is a floating input or a high output
and any I/O bit shown as a 1 is an input tied to ground or a low output.