User Manual

IOB Hardware Reference Theory of Operation
CTI Products, Inc.
68-11168-105
13
Creating Eight Sub-categories
To create eight sub-categories, three I/O bits must be reserved for the sub-category
selector. In Table 10, I/O bits 2, 3 and 4 have been reserved for the sub-category
selector. You can see from the table that there are two possible status messages
that can be defined for each sub-category. Because I/O bits 2, 3 and 4 have been
reserved as the selector, all IOB pins that correspond to I/O bits 2, 3 and 4 cannot
be used by application circuitry.
Warning: Because I/O bit 3 is used as a sub-category selector, you must make
sure that the mouse and keyboard button cannot change the state of the I/O pins
corresponding to I/O bit 3. Therefore, in your category definition, make sure the
DISABLE=x line state the following:
DISABLE=O
This line will turn off the right mouse button and the ‘D’ keyboard key so that I/O
bit 3 cannot be controlled from the keyboard.
Input Value
Field
Sub-
category
#
Sub-category
Selector I/O Bits
4 3 2
I/O Bit
Combinations
1
00 1 0 0 0 0
01 1 0 0 0 1
04 2 0 0 1 0
05 2 0 0 1 1
10 3 0 1 0 0
11 3 0 1 0 1
14 4 0 1 1 0
15 4 0 1 1 1
40 5 1 0 0 0
41 5 1 0 0 1
44 6 1 0 1 0
45 6 1 0 1 1
50 7 1 1 0 0
51 7 1 1 0 1
54 8 1 1 1 0
55 8 1 1 1 1
Table 11 - 8 Sub-categories / 2 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.