GE Multilin F650, Instruction Manual

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APPENDIX B: MODBUS PROTOCOL B.4 MODBUS DATA
GEK-106310-AF F650 DIGITAL BAY CONTROLLER B-17
For reading the oscillography in several strings, several reading requests must be sent to 0xff40 address. For reading the
previous message a reading petition must be sent to 0xff42 address. The maximum number of bytes to be read in each
part is 244.
Note: For firmware versions 7.xx and above, this feature is not available.
B.4.10 Time synchronization
Time synchronization consists of setting the relay date and time.
This is similar to other settings group entries, with some unique characteristics:
- The data type is specific to time.
- Once the data is changed, varies with time, it is a changing setting that can be read.
- It shares the time change with IRIG-B (this has more priority) and with a possible modification from MMI or another
protocols.
- When the relay is disconnected from its auxiliary power supply for extended periods (days) the time remains in a
chip, fed by a capacitor (it does not need maintenance).
- And last, there are synchronism between the real time chip and the microprocessor time.
Time synchronization is made by a reading message over 0xfff0 address, either with the address of a single relay, if a
writing confirmation is desired, or in broadcast, to synchronize several relays simultaneously.
Date/time format is stored in 4 MODBUS registers (8 bytes, Big Endian format), which indicates elapsed milliseconds from
the 1
st
of January 2000 at 00:00:00.000.
Reading example:
[0xFE 0x03 0xFF 0xF0 0x00 0x04 0x60 0x21] ---------> RELAY
PC <---------- [0xFE 0x03 0x08 0x00 0x00 0x00 0x17 0x05 0xFA 0xD5 0xBA 0x2D 0x1D]
Synchronism example:
[0xFE 0x10 0xFF 0xF0 0x00 0x04 0x08 0x00 0x00 0x00 0x17 0x9B 0x53 0x3F 0x60 0xA4 0x2B] ---------> RELAY
PC <---------- [0xFE 0x10 0xFF 0xF0 0x00 0x04 0xE5 0xE2]
B.4.11 Queueing messages
In ModBus protocol, as in other protocols, exists an internal procedure in message reception and transmission.
When a relay gets a string, determined by a silence of 3 or 4 characters, it is queued in a FIFO queue, for a later processing
in its own protocol. When the protocol is free of execution, it searches in the queue for strings to respond of the FIFO. If
there is such string, it processes it and then it is responded.
Several criteria have been adopted for real time operation:
- Each reading or writing is answered as soon as possible.
- This implies that when settings are changed and answered, a writing request recognition is indicated and then, the
modification of internal settings is performed, and finally, after confirmation is sent, settings are stored in a non-
volatile memory device.
NOTE: As the relay is internally a modular system, it is possible that the response of some processes is slower than what is
expected by the external program, considering the message as missed and sending again another request. If so, there will
be 2 queued messages and therefore, 2 message responses. For this reason, response message ‘ACK’ must be verified