GE 269Plus

GE Power Management 269Plus Motor Management Relay 4- 7
4 COMMUNICATIONS EXCEPTION OR ERROR REPLIES
4
4.7 EXCEPTION OR ERROR REPLIES
When the master command cannot be performed, the 269Plus replies with an error code. This is different from
detecting communication related errors, such as CRC error for which the 269Plus ignores the command.
The format of an error reply is to return the received address and function back to the master with most signifi-
cant bit of the function code set. Also, a one byte error code is added to the reply packet to identify the prob-
lem. The error codes supported by the 269Plus are:
• 01: illegal function
• 02: register address out of range or start register + register count = register address out of range
• 03: register count is out of range
There is no range checking on 269Plus setpoint values, Therefore, extra care must be taken when
writing setpoints directly to the memory map to ensure they are within range.
For example, the master requests reading an actual value register by sending the following data block:
The actual value register 05A1h does not exist in the 269Plus. Therefore, it replies with the data block:
SLAVE
ADDRESS
FUNCTION
DATA BYTES
CRC
(low, high)
START REG COUNT
11h 04h 05h A1h 00h 01h 62h 74h
SLAVE
ADDRESS
FUNCTION
with MSB set
ERROR CODE
CRC
(low, high)
11h 84h 02h C3h 04h
NOTE