Home About MODBUS fc01 fc02 fc03 fc04 fc05 fc06 fc15 fc16 ASCII TCP exceptions About Enron MODBUS RTU Master RTU Slave TCP Client Download Purchase Contact Read Coil Status (FC=01) Request This command is requesting the ON/OFF status of discrete coils # 20 to 56 from the slave device with address 17. 11 01 0013 0025 0E84 11: The Slave Address (17 = 11 hex) 01: The Function Code (read Coil Status) 0013: The Data Address of the first coil to read. (Coil 20 - 1 = 19 = 13 hex) 0025: The total number of coils requested. (coils 20 to 56 = 37 = 25 hex) 0E84: The CRC (cyclic redundancy check) for error checking. Response 11 01 05 CD6BB20E1B 45E6 11: The Slave Address (17 = 11 hex) 01: The Function Code (read Coil Status) 05: The number of data bytes to follow (37 Coils / 8 bits per byte = 5 bytes) CD: Coils 27 - 20 (1100 1101) 6B: Coils 35 - 28 (0110 1011) B2: Coils 43 - 36 (1011 0010) 0E: Coils 51 - 44 (0000 1110) 1B: 3 space holders & Coils 56 - 52 (0001 1011) 45E6: The CRC (cyclic redundancy check). The more significant bits contain the higher coil variables. This shows that coil 36 is off (0) and 43 is on (1). Due to the number of coils requested, the last data field1B contains the status of only 5 coils. The three most significant bits in this data field are filled in with zeroes. Home • FAQ • Enron • Download • Purchase • Contact Copyright © 2013 Simply Modbus. All rights reserved Simply Modbus - Function Code 01 - Read Coil Status http://www.simplymodbus.ca/FC01.htm 1 of 1 3/5/2015 8:55 PM

Simply Modbus - Function Code 01 - Read Coil Status

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Read Coil Status (FC=01)Request

This command is requesting the ON/OFF status of discrete coils # 20 to 56from the slave device with address 17.

11 01 0013 0025 0E84

11: The Slave Address (17 = 11 hex)01: The Function Code (read Coil Status)0013: The Data Address of the first coil to read. (Coil 20 - 1 = 19 = 13 hex)0025: The total number of coils requested. (coils 20 to 56 = 37 = 25 hex) 0E84: The CRC (cyclic redundancy check) for error checking.

Response

11 01 05 CD6BB20E1B 45E6

11: The Slave Address (17 = 11 hex)01: The Function Code (read Coil Status)05: The number of data bytes to follow (37 Coils / 8 bits per byte = 5 bytes)CD: Coils 27 - 20 (1100 1101)6B: Coils 35 - 28 (0110 1011)B2: Coils 43 - 36 (1011 0010)0E: Coils 51 - 44 (0000 1110)1B: 3 space holders & Coils 56 - 52 (0001 1011)45E6: The CRC (cyclic redundancy check).

The more significant bits contain the higher coil variables. This shows that coil 36 isoff (0) and 43 is on (1). Due to the number of coils requested, the last data field1Bcontains the status of only 5 coils. The three most significant bits in this data fieldare filled in with zeroes.

Home FAQ Enron Download Purchase ContactCopyright 2013 Simply Modbus. All rights reserved

Simply Modbus - Function Code 01 - Read Coil Status http://www.simplymodbus.ca/FC01.htm

1 of 1 3/5/2015 8:55 PM