Technical Manual for EA350 Analog Pulse Type Servo Driver V101 Chapter 10 Communication protocol 10.1 Scope of application 1. Applicable series: EA350 series servo driver. 2. Applicable network: “Single-master multi-slave” communication network with MODBUS-RTU protocol and RS485 bus. A typical RTU message frame format as shown below: 10.2 Physical interface RS485 asynchronous half-duplex communication mode. Default data format of RS485 terminal: 1-8-N-1, baud rate: 9600bps. Data formats 1-8-N-1/2, 1-8-O-1/2 and 1-8-E-1/2, and baud rates 4800bps, 9600bps, 19200bps, 38400bps, 57600bps and 115200bps are available for selection through function codes P7-01 and P7-02.
10.3 Protocol format Check in ADU(Application Data Unit) is derived from high-low byte swap of the CRC16 checksum of the first three parts in ADU. In the protocol format, the low byte of CRC check is in front of the high byte. 10.4 Command explanation Command code 0x03: Read a function code of the servo driver Command code 0x06: Write a single function code of the servo driver 238 Start Bit Equipment address Function code Data CRC check End mark T1-T2-T3-T4 8Bit 8Bit n*8Bit 16Bit T1-T2-T3-T4 Details of the ADU part Number of bytes Scope Request sent by the host:
Slave address 1 0x00-0xFEH Command code 1 0x03 Starting address of register 2 0x0000-0xFFFF Number of registers 2 0x0001-0x0022 CRC check (low byte in front) 2 Slave acknowledgement: Slave address 1 Address of the unit Command code 1 0x03 Number of bytes read 1 2 * number of registers Register content 2 * number of registers CRC check 2 Details of the ADU part Number of bytes Scope Request sent by the host: Slave address 1 0x00-0xFEH Command code 1 0x06 Address of register 2 0x0000-0xFFFF Register content 2 0x0000-0xFFFF CRC check 2 Slave acknowledgement: Slave address 1 Address of the unit Command code 1 0x06 Address of register 2 0x0000-0xFFFF Register content 2 0x0000-0xFFFF CRC check 2