B-14 F650 DIGITAL BAY CONTROLLER GEK-106310-AF
B.4 MODBUS DATA APPENDIX B: MODBUS PROTOCOL
B.4.6.2 Event collection process
ALL EVENTS
Whe n reading all events, there are two possible approaches:
First option: start from the oldest event, in address 0xFCFF, and read the events 15 by 15. The initial request frame sent to
the relay is as follows:
Within this frame the buffer pointer is set to the oldest event, or number 7421 in the example. 15 events are returned,
ending with number 7435.
In order to read the following 15 events, numbered from 7436 to 7450, calculate the initial address and send another
request frame:
Hex(7436)= 0x1D0C
0x1D0C AND 0x00FF= 0xOC
0xFD00+0x0C= 0xFD0C: initial address
[0xFE 0x03 0xFD 0x0C 0x00 0x69 0x60 0x44] ---------> RELAY
Either continue until the relay responds with a 0 event, or stop at the last recorded event by reading the number of the
next upcoming event from address 0x03FF and comparing against the last event read.
Second option: read the circular event queue directly, from address 0xFD00 to 0xFDFF, and then rearrange the retrieved
events by event number.
Once all events have been read, subsequent queries should only request new events.
NEW EVENTS
The 0x03FF address contains the number of the next event to be written. Based on this, the number of events recorded
since the last query can be determined.For example, if the relay indicates that the next event to be generated is number
7677 and events up to number 7674 have already been read, there are two new events. A frame must be sent to read the
two new events, 7675 and 7676, and the corresponding 28 bytes.
NOTE: In this example the 0x03FF address has event number 7677 because 7676 was the last event number used.
Hex(7675)=0x1DFB
0x1DFB AND 0xFF=0xFB
0xFD00+0xFB=0xFDFB: reading address (*)
[0xFE 0x03 0xFD 0xFB 0x00 0x0E 0x90 0x5C] ---------> RELAY
Event
Number
7424 7425 .......... 7675 7676 7421 7422 7423
Address 0xFD00 0xFD01 0xFDFB 0xFDFC 0xFDFD 0xFDFE 0xFDFF
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