P92x/EN CT/E11 Technical Guide
Modbus Protocol
Page 10/118 MiCOM P921-P922-P923
1.4.2 Service request
This request shall be send before to retrieve the sample data of a disturbance record
channel. It allows to specify the record number and the channel number which have
to be retrieved. It allows also to know the number of samples in the channel.
Slave number Function code Word address Word number CRC
xx 03h Refer to
mapping
00 0Bh xx.........xx
This request may be answered an error message. Two error codes are possible :
CODE_DEF_RAM (02) : Saved RAM failure.
CODE_EVT_NOK (03) : No disturbance record available in the saved
RAM.
1.4.3 Request to retrieve the data of a disturbance record channel
Slave number Function code Word address Word number CRC
xx 03h Refer to mapping 1 to 7Dh xx......xx
This request may be answered an error message. Two error codes are possible :
CODE_DEP_DATA (04) : The requested sample number is superior than
the number of samples in the specified
channel.
CODE_SERV_NOK (05) : The record number and the channel number
have not been specified by a service request.
NOTA : This type of request can retrieve up to125 words. A sample is
coded on 1 word (16 bits).
1.4.4 Request to retrieve an index frame
Slave number Function code Word address Word number CRC
xx 03h 22h 00 00 07h xx........xx
This event request may be answered an error message with the error code :
CODE_SERV_NOK (05) : The record number and the channel number
have not been specified by a service request.
1.5 Modbus request definition used to retrieve the event records
Two ways can be followed to retrieve an event record :
1. Send a request to retrieve the oldest non-acknowledge event.
2. Send a request to retrieve a dedicated event.
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