User Manual

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.