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5.1.MODBUS-RTU transmission format
5.1.1. Read command (03)
Computer → Inverter *The text size is 8 bytes fixed.
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| Commu- | Commu- | Number | Number | CRC | CRC |
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(3.5bytes | Inverter | Command | nication | nication | of Data | of Data | (3.5bytes | ||
Blank) | No. |
| No. | No. | Groups | Groups | (low) | (high) | Blank) |
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| (high) | (low) | (high) | (low) |
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| 03 |
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| 00 | 01 |
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1) Inverter No.. (1 byte)
:Specify an inverter number between 0 and 247 (00H to F7H).
Command processing will be executed only broadcast communication “0” and with those inverters that match set inverter numbers. Data will not be returned if “0” (broadcast communication) and inverter numbers do not match.
2) | Command (1 byte) | : Set the read command (03H fixed). |
3) | Communication No.. (2 bytes) | : Set in the order of high to low numbers. |
4) | Number of data groups (2 bytes) | : Set the number of data words 0001 (fixed) in the order of high to low numbers. |
5) | CRC (2 bytes) | : Set generation results of CRC in the order of low to high numbers.. For the |
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| method to generate CRC, see “5.2 CRC Generation.” Note that the setting se- |
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| quence is reversal to that of others. |
Inverter → Computer (Normal return) *The text size is 7 bytes fixed.
(3.5bytes
Blank)
Inverter | Command | Number of | Read data | Read data | CRC | CRC |
No. |
| Data | (high) | (low) | (low) | (high) |
| 03 | 02 |
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(3.5bytes
Blank)
1) | Command (1 byte) | : Read command (03H fixed) will be returned. |
2) | Number of data | : A number of data bytes (02H fixed) will be returned. |
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| transmission to the inverters is 2 bytes and 01H fixed. |
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| turned by the inverters is 1 byte and 02H fixed. |
The number of data groups for Note that the number of data re-
3) Read data (2 bytes) : Returned in the order of read data (high) and (low).
Inverter → Computer (Abnormal return) *The text size is 5 bytes fixed.
(3.5bytes
Blank)
Inverter No. | Command | Error Code | CRC | CRC | |
(low) | (high) | ||||
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| 83 |
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(3.5bytes
Blank)
1) | Command (1 byte) | : 83H fixed (Read command error) (Command + 80H) | |
2) | Error code (1 byte) | : See “4.3 Transmission errors.” | |
Example: Reading output frequency (During 60Hz operation) | |||
(Computer → inverter) | 01 03 | FD 00 00 01 B5 A6 | |
(Inverter → computer) | 01 03 | 02 17 70 B6 50 | |
Example: Data specification error
(Computer → inverter) | 01 03 | FD 00 00 02 F5 A7 |
(Inverter → computer) | 01 83 | 03 01 31 |
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