Siemens RS-485 manual Checksum CRC16, Crc = Shr Crc, Reply CRC16 =, Function number

Page 6

Checksum (CRC16)

Calculation

Example

The checksum (CRC16) is used to detect transmission errors.

If the evaluation reveals an error, the relevant device will not respond.

CRC = 0xFFF

CRC = CRC XOR ByteOfMessage

For (1 to 8)

if (flag to the right = 1)

thenelse

CRC = CRC XOR 0xA001

while (not all ByteOfMessage edited)

The low byte of the checksum will be transmitted first.

Data query:

Reading 2 words from address 6 (CRC16 = 0x24A0)

CRC16

0B	03	04	00		00	42		C8	61		05
				Word 1			Word 2			CRC16

6/14

Siemens Building Technologies	CC1A7865.1en
HVAC Products	31.10.2002

Image 6

Contents Master-slave principle 31.10.2002Transmission mode RTU NotDevice address Baud rate Communication sequenceReply by the slave 600 813 19.200 406Communication during the slave’s internal handling time Data query sequenceTime sequence Communication during the slave’s response timeFunction code Fault handlingSlave address Data fieldReply CRC16 = Checksum CRC16CRC = SHR CRC Following functions for the device will be availableReading n words Writing 1 wordReply Example Write switch-on threshold Hys1 = Word address =Writing n words Instruction AddressAddress Data Access Parameter Value range Default Access ParameterAddress tables Roff TempREM SetpointAddress Data type Access Parameter Device stateDescription of operating modes «FULLY REMOTE» SPRRemote RK1 Operating mode Floating output with Dependent switchingControl strategy for Modulating burner