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4. Communications
4.5 Command Code
4.5.1 Command Code: 01, Read Status of Contact (Input point X is not included)
Number of Points (max) = 255 (Dec) = FF (Hex)
ExampleRead contacts T20~T56 from Slave ID#1
PCPLC “:01 01 06 14 00 25 BF CR LF”
Sent message:
Field Name ASCII
STX :
Slave Address 01
Command code 01
Starting Address Hi 06
Starting Address Lo 14
Number of Points Hi 00
Number of Points Lo 25
Error Check (LRC) BF
ETX 1 0D (Hex)
ETX 0 0A (Hex)
Assume Number of Points in sent message is n (Dec), quotient of n/8 is M and the remainder is N.
When N = 0, Bytes Count in feedback message will be M; when N0, Bytes Count will be M+1.
PLCPC “:01 01 05 CD 6B B2 0E 1B D6 CR LF”
Feedback message:
Field Name ASCII
STX :
Slave Address 01
Command code 01
Bytes Count 05
Data (Coils T27…T20) CD
Data (Coils T35…T38) 6B
Data (Coils T43…T36) B2
Data (Coils T51…T44) 0E
Data (Coils T56…T52) 1B
Error Check (LRC) E6
END 1 0D (Hex)
END 0 0A (Hex)
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