Diagnostics - GE ASTAT XT QT 0008U Series User Manual

Example 9:
To read all discrete inputs of ASTAT-XT # 12, the host computer sends the following Query frame:
byte 1: Serial Link No.
byte 2: Function
byte 3: Starting Address High ($00)
byte 4: Starting Address Low ($00)
byte 5: No. of Points High
byte 6: No. of points Low
byte 7: CRC_Low
byte 8: CRC_High
The ASTAT-XT response when only Stop and Soft Stop terminals (Inputs 1&2) are connected:
byte 1: Serial Link No.
byte 2: Function
byte 3: Byte Count
byte 4: Data (Inputs 7..0)
byte 5: CRC_Low
byte 6: CRC_High
A.12.

Diagnostics

Modbus Function 08 as implemented in the ASTAT-XT supports only Subfunction $0000. It provides for the
"loopback" (Return Query Data) feature, and for checking the Communication Serial Link between the master and
the ASTAT-XT.
To request ASTAT-XT # 1 to return Query data, the master should send following Query frame:
byte 1: Serial Link No.
byte 2: Function
byte 3: Subfunction High
byte 4: Subfunction Low
byte 5: Data High
byte 6: Data Low
byte 7: CRC_Low
byte 8: CRC_High
The Normal (if no exception) response is the echo of the Query:
byte 1: Serial Link No.
byte 2: Function
byte 3: Subfunction High
byte 4: Subfunction Low
byte 5: Force Data High
byte 6: Force Data Low
byte 7: CRC_Low
byte 8: CRC_High
• Appendix A - MODBUS RTU Protocol
98
($0C) (12)
($02)
($00)
$08)
($XX)
($XX)
($0C) (12)
($02)
($01)
($03)
($XX)
($XX)
($01)
($08)
($00)
($00)
($37)
($A5)
($XX)
($XX)
($01)
($08)
($00)
($00)
($37)
($A5)
($XX)
($XX)