Creating four sub-categories, Table 10 - 4 sub-categories / 4 states – CTI Products IOB I/O Interface User Manual
Page 17
IOB Hardware Reference
Theory of Operation
CTI Products, Inc.
68-11168-105
12
Creating Four Sub-categories
To create four sub-categories (for four different I/O types), two I/O bits must be
reserved for the sub-category selector. In Table 10, I/O bits 3 and 4 have been
reserved for the sub-category selector. You can see from the table that there are
four possible status messages that can be defined for each sub-category. Because
I/O bits 3 and 4 have been reserved as the selector, all IOB pins that correspond to
I/O bits 3 and 4 in all I/O groups 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
I/O Bit
Combinations
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
2
0 1
0 0
11
2
0 1
0 1
14
2
0 1
1 0
15
2
0 1
1 1
40
3
1 0
0 0
41
3
1 0
0 1
44
3
1 0
1 0
45
3
1 0
1 1
50
4
1 1
0 0
51
4
1 1
0 1
54
4
1 1
1 0
55
4
1 1
1 1
Table 10 - 4 Sub-categories / 4 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.