Management byte
Bits 0 – 3 contain the service identifier and define the service to be executed.
Bits 4 and 5 specify the data length in bytes. The data length for SEW frequency inverters should be set to 4 bytes.
Byte 0: Management | ||||||||||||||||||
data | LSB | |||||||||||||||||
Bit: | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | ||||||||||
| Service identifier: 0000 = No service 0001 = Read parameter 0010 = Write parameter 0011 = Write parameter volatile 0100 = Read minimum 0101 = Read maximum 0110 = Read default 0111 = Read scale 1000 = Read attribute | |||||||||||||||||
| Data length: 00 = 1 byte 01 = 2 bytes 10 = 3 bytes 11 = 4 bytes | |||||||||||||||||
| Handshake bit | |||||||||||||||||
Status bit: 0 = No error while executing service 1 = Error while executing service | ||||||||||||||||||
Bit 6 is the handshake bit. It has a different meaning depending on the bus system:
- With SBus 1 (CAN) and set handshake bit (= 1), the response telegram is sent after the synchronization telegram.
- With RS485 and fieldbus, the handshake bit serves as acknowledgement bit between client and server when using the cyclic transmission method. As the parameter channel is transmitted cyclically in this variant, probably with the process data, the implementation of the service in the inverter must be triggered by edge control using handshake bit 6. For this purpose, the value of this bit is toggled for each new service to be executed. The inverter uses the handshake bit to signal whether the service has been executed or not. The service has been executed as soon as the handshake bit received in the controller is identical with the transmitted handshake bit.
Status bit 7 indicates whether the service was executed properly or whether errors occurred.
