Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Manual do Utilizador descarregar pdf (Página 140)

9–2 Diagnostic Counters

Publication

17706.5.16 - 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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Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Manual do Utilizador Página 140