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Appendix A - MODBUS RTU Protocol
Example 9:
To read all discrete inputs of ASTAT-XT # 12, the host computer sends the following Query frame:
byte 1: Serial Link No.
($0C) (12)
byte 2: Function
($02)
byte 3: Starting Address High ($00)
byte 4: Starting Address Low ($00)
byte 5: No. of Points High
($00)
byte 6: No. of points Low
$08)
byte 7: CRC_Low
($XX)
byte 8: CRC_High
($XX)
The ASTAT-XT response when only Stop and Soft Stop terminals (Inputs 1&2) are connected:
byte 1: Serial Link No.
($0C)
(12)
byte 2: Function
($02)
byte 3: Byte Count
($01)
byte 4: Data (Inputs 7..0)
($03)
byte 5: CRC_Low
($XX)
byte 6: CRC_High
($XX)
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.
($01)
byte 2: Function
($08)
byte 3: Subfunction High
($00)
byte 4: Subfunction Low
($00)
byte 5: Data High
($37)
byte 6: Data Low
($A5)
byte 7: CRC_Low
($XX)
byte 8: CRC_High
($XX)
The Normal (if no exception) response is the echo of the Query:
byte 1: Serial Link No.
($01)
byte 2: Function
($08)
byte 3: Subfunction High
($00)
byte 4: Subfunction Low
($00)
byte 5: Force Data High
($37)
byte 6: Force Data Low
($A5)
byte 7: CRC_Low
($XX)
byte 8: CRC_High
($XX)
Содержание ASTAT XT QT 0008U Series
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Страница 17: ...17 Technical Specifications 3 4 I O Wiring...
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