CTI Products IOB I/O Interface - Manual (Page 14)

IOB Hardware Reference Theory of Operation
CTI Products, Inc.
68-11168-105
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This option is typically used when you need 1 of 4 relays that will operate in a
fail-safe mode when the power fails. For instance, you can drive 4 DPDT relays
to provide a 1 of 4 manual transmitter selection circuit. Transmitters 2 through 4
would be connected to the normally open relay contacts, while transmitter 1
would be connected to the normally closed contacts. If the power fails, the system
will revert to transmitter 1.
3.4 Mode 3 - One Set of 1 of 4 Select Outputs
+ 8 Independent Outputs
In this mode, the IOB provides one bank of 1 of 4 Select output lines, 8
input/output lines and 20 input only lines. Table 16 shows the pinout for this
mode as well as the I/O group and I/O bit number associated with each connector
pin.
The first 4 I/O groups are used as 1 of 4. I/O groups 5 through 8 are independent
I/Os. The operation of the first 4 I/O groups is the same as Mode 2.
3.5 Mode 4 - One Set of 1 of 8 Select Outputs
In this mode, the IOB provides a 1 of 8 Select output and 24 input only lines.
Table 16 shows the pinout for this mode as well as the I/O group and I/O bit
number associated with each connector pin.
Table 7 shows how the 1 of 8 Select outputs operate, allowing only one active
output in each the of 8 Select lines (A through H).
Select
A B C D E F G H
selected output
1 0 0 0 0 0 0 0 Select A
0 1 0 0 0 0 0 0 Select B
0 0 1 0 0 0 0 0 Select C
0 0 0 1 0 0 0 0 Select D
0 0 0 0 1 0 0 0 Select E
0 0 0 0 0 1 0 0 Select F
0 0 0 0 0 0 1 0 Select G
0 0 0 0 0 0 0 1 Select H
Table 7 - 1 of 8 Select Operation
Note: In this table, any output shown as a 0 is a high output and any output shown
as a 1 is low output.
The IOB has the option to invert the Select A output so that the Select A output
pin is active high and the Select B, C and D output pins are active low. This