Chapter Six: RS-232 Communications Option
RS-232 Messages
99
Example 2: How To Test the Output Signals on the I/O Connector
This diagnostic test allows you to set the values of the output signals on the I/O connector. Use a
voltmeter to read the value of the signals at the connector to detect any problem. This command
controls the 8 outputs on the I/O connector. Table 25 lists the output bit number assignments
and the bit values. To determine the connector value, add the bit values of the bits you wish to
pull low. A value of 255 will set all the outputs low. Enter the connector value as the <data>
field in the command string.
1. Calculate the connector value by adding the value of the bits you wish to pull low, in this
case bits 3 (Channel 1 selected) and 5 (x1 range):
4 + 16 = 20
Value of bit 3
Value of bit 5
Connector value
2. Issue the following command:
@80220
ENTER
3. Use a voltmeter to measure the output signals on pins 29 and 23 of the I/O connector.
Each pin should be close to 0.00 V.
I/O Connector Output Bit Number Assignments
Diagnostic Output
Bit Number
Bit Value
Function
I/O Pin
Number
1
1
Not Used
—
2
2
Not Used
—
3
4
Select Channel 1 *
29
4
8
Select Channel 2 *
28
5
16
x1 Range ID
23
6
32
x0.1 Range ID
19
7
64
x0.01 Range ID
18
8
128
Reserved
17
* The 274 multiplexer uses these pins select the active channel. Both
pins 28 and 29 high when Channel 3 is the active channel.
Table 25: I/O Connector Output Bit Assignment
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