Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 140)

9–2 Diagnostic Counters
Publication 1770Ć6.5.16 - October 1996
Reading diagnostic counters
To read diagnostic counters, you issue a diagnostic read command
from a device that:
•
is connected to an interface module that supports an
asynchronous port
•
can format the diagnostic commands
(Therefore, a PLC user program is unable to initiate a diagnostic
command.)
An interface module’s diagnostic counter location varies:
•
by module type
•
between revision levels of the same type module
You first request the location of these counters by transmitting a
diagnostic status command to the module. (For more on diagnostic
status, see page
7–6 .) Based on the address returned, you can use the
number of the counters which follow as an offset to calculate:
•
the location of the desired counter
•
how many counter values you want returned
You can then use this information to format a diagnostic read
command. The reply from the diagnostic read command contains
the data stored in the counters. For the PLC-5 and SLC 500
processors, you format the diagnostic read command with a dummy
value for the address. The reply contains the entire counter block.
(For more on diagnostic read, see page
7–19 .)
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