Writing SPA data refers here either to writing to a Modbus coil (one bit data) or to a writable Modbus register (up to 16 bit data). SPA write operation can only be performed to one Modbus object at a time.
There are rules for writing SPA data.
- When writing to coils, SPA channel 0 is used. Data type is O, and the data number corresponds to the coil address to be written. Value can be “0” or “1” (depends on the object).
- When writing to registers, SPA channel 1 is used. Data type is O, and the data number corresponds to the register address to be written. Value can be 0...65535 (depends on the object).
If the written data address does not exist in the protection relay, there is a negative SPA response (NAK) number 6. If the value is rejected by the Modbus object then the negative SPA response number is 8. A successful writing is positively acknowledged.
Writing the value “1” to the Modbus coil address 2052 (if the SPA channel is 0, the channel number is omitted in the command message):
>25WO2052:1:CC <25A:CCWriting the value “7” to the Modbus register address 9051:
>25W1O9051:7:CC <25A:CC