Reading n words
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| This function is used to read n words from a certain address. |
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Data query |
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Slave address | Function 0x03 | Address of the |
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| Checksum | ||||||||||||||||
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| or 0x04 |
| first word |
| words |
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| (max. 12) |
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| 1 byte |
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| 2 bytes |
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Reply |
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Slave address | Function 0x03 |
| Number of | Word value(s) | Checksum | |||||||||||||||||
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| or 0x04 |
| bytes read |
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| CRC16 | |||||||
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| 1 byte |
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| x byte(s) |
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Example | Reading the 2 setpoints of the controller |
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| Word address = 0x0008 (setpoint SP1) |
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| Data query: |
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| 0B |
| 03 |
| 00 |
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| 08 |
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| 04 |
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| CRC16 | ||||
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| Reply: |
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| 0B |
| 03 | 08 |
| 0000 |
| 42C8 |
| 0000 |
| 4316 |
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| Setpoint 1 (100) |
| Setpoint 2 (150) |
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Writing 1 word |
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| With the “Wordwriting” function, the data blocks for instruction and reply are identical. | ||||||||||||||||||||
Instruction |
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Slave address | Function 0x06 | Word address |
| Word value |
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| CRC16 | ||
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| 1 byte |
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| 2 bytes |
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| 2 bytes | ||||||||||
Reply |
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Slave address | Function 0x06 | Word address |
| Word value |
| Checksum | ||||||||||||||||
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| CRC16 | ||
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| 1 byte |
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Example | Write limit value limit comparator 1 (AL1) (= 275) |
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| Word address = 0x000C |
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| Instruction: (write the first part of the value) |
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| 0B |
| 06 |
| 00 |
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| 0C |
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| 80 |
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| 00 |
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| CRC16 | ||||
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| Reply (like instruction): |
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| 0B |
| 06 |
| 00 |
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| 0C |
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| 80 |
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| 00 |
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| CRC16 | ||||
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| Instruction: (write the second part of the value) |
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| 0B |
| 06 |
| 00 |
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| 0D |
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| 43 |
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| 89 |
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| CRC16 | ||||
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| Reply (like instruction): |
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| 0B |
| 06 |
| 00 |
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| 0D |
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| 43 |
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| 89 |
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| CRC16 | ||||
| 7/14 |
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Siemens Building Technologies | CC1A7865.1en |
HVAC Products | 31.10.2002 |
