GE 750 User Manual

GE Power Management 750/760 Feeder Management Relay 16-
11
16 COMMUNICATIONS 16.3 MODBUS PROTOCOL
16
16.3.10 EXCEPTION RESPONSES
Programming or operation errors happen because of illegal data in a packet, hardware or software problems in
the slave device, etc. These errors result in an exception response from the slave. The GE Power Manage-
ment 750/760 implements the error codes listed in Table 16–9: EXCEPTION RESPONSE ERROR CODES on
page 16–11. The slave detecting one of these errors sends a response packet to the master with the high order
bit of the function code set to 1.
The following table shows the format of the master and slave packets. The example shows a master device
sending the unsupported function code 39h to slave device 11.
Table 16–8: MASTER/SLAVE PACKET FORMAT FOR UNSUPPORTED FUNCTION CODE
MASTER TRANSMISSION SLAVE RESPONSE
PACKET FORMAT EXAMPLE (HEX) PACKET FORMAT EXAMPLE (HEX)
SLAVE ADDRESS 11 SLAVE ADDRESS 11
FUNCTION CODE 39 FUNCTION CODE B9
CRC - low order byte CD ERROR CODE 01
CRC - high order byte F2 CRC - low order byte 93
CRC - high order byte 95
Table 16–9: EXCEPTION RESPONSE ERROR CODES
ERROR
CODE
MODBUS DEFINITION GE POWER MANAGEMENT IMPLEMENTATION
01 ILLEGAL FUNCTION The function code of the master query packet is not a function
code supported by the slave.
02 ILLEGAL DATA
ADDRESS
The address referenced in the data field of the master query
packet is not an address supported by the slave.
03 ILLEGAL DATA VALUE The value referenced in the data field of the master query packet is
not allowable in the addressed slave location.
04 FAILURE IN
ASSOCIATED DEVICE
The addressed slave has internal failure which prevents it from
performing the action as requested.
05
†
ACKNOWLEDGE The addressed slave device has accepted and is processing a
long duration command. Poll for status.
06
†
BUSY, REJECTED
PACKET
The packet was received without error, but the slave device is
engaged in processing a long duration command. Retransmit later,
when the slave device may be free.
07
†
NAK - NEGATIVE
ACKNOWLEDGE
The packet was received without error, but the request could not
be performed, because this version of the 750/760 does not have
the requested operation available.
†
Some implementations of Modbus may not support these exception responses.

GE 750 Specifications

General

Brand	GE
Model	750
Category	Relays
Language	English