Creating eight sub-categories, Table 11 - 8 sub-categories / 2 states – CTI Products IOB I/O Interface User Manual
Page 18
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.