Rockwell Automation 1769-OF4VI Compact I/O Isolated Analog Modules - Manual (Page 58)

Publication 1769-UM014B-EN-P - May 2010
4-6 Module Data, Status, and Channel Configuration for the Output Modules
1769-OF4CI and -OF4VI Output Data Loopback/Echo
Words 2 to 5 provide output loopback/data echo through the Input Data file
for channels 0 to 3. The value of the data echo is the analog value currently
being converted on-board the module by the D/A converter. This ensures that
the logic-directed state of the output is true. Otherwise, the state of the output
could vary depending on controller mode.
Under normal operating conditions, the data echo value is the same value that
is being sent from the controller to the output module. Under abnormal
conditions, the values may differ.
EXAMPLE
 During run mode, the control program could direct the
module to a value over or under the defined full range.
In that case, the module raises the over- or under-range
flag and continues to convert and data echo up to the
defined full range. However, upon reaching either the
maximum upper or lower full range value, the module
stops converting and echoes back that maximum upper
or lower full range value, not the value being sent from
the controller.
 During program or fault mode with Hold Last State or
User-Defined Value selected, the module echoes the
hold last value or alternate value you selected. For more
information on the hold last and user-defined values,
see 1769-OF4CI and -OF4VI Fault Value on page 4-15
and 1769-OF4CI and -OF4VI Program/Idle Value on
page 4-16.
 When one or more of the output channel’s Output
Held bits are set (1). See 1769-OF4CI and -OF4VI
Output Held Bits (H0 to H3) on page 4-5.