Siemens RS-485 - Data Read and Write Functions; Reading n Words; Writing 1 Word

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Siemens Building Technologies CC1A7865.1en
HVAC Products 31.10.2002
Reading n words
This function is used to read n words from a certain address.
Slave address Function 0x03
or 0x04
Address of the
first word
Number of
words
(max. 12)
Checksum
CRC16
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Slave address Function 0x03
or 0x04
Number of
bytes read
Word value(s) Checksum
CRC16
1 byte 1 byte 1 byte x byte(s) 2 bytes
Reading the 2 setpoints of the controller
Word address = 0x0008 (setpoint SP1)
Data query:
0B 03 00 08 00 04 CRC16
Reply:
0B 03 08 0000 42C8 0000 4316 CRC16
Setpoint 1 (100) Setpoint 2 (150)
Writing 1 word
With the “Wordwriting” function, the data blocks for instruction and reply are identical.
Slave address Function 0x06 Word address Word value Checksum
CRC16
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Slave address Function 0x06 Word address Word value Checksum
CRC16
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Write limit value limit comparator 1 (AL1) (= 275)
Word address = 0x000C
Instruction: (write the first part of the value)
0B 06 00 0C 80 00 CRC16
Reply (like instruction):
0B 06 00 0C 80 00 CRC16
Instruction: (write the second part of the value)
0B 06 00 0D 43 89 CRC16
Reply (like instruction):
0B 06 00 0D 43 89 CRC16
Data query
Reply
Example
Instruction
Reply
Example