26
®
COMMUNICATIONS
The protocol to be used is Modbus RTU. This is implemented by the master (PC, PLC, etc.) issuing a
poll to the slave (Flame-Monitor) and the slave responding with the appropriate message.
A typical format of a poll request is as follows:
DST refers to the logical address of the slave.
FNC is the function being requested. FNC 03 is a read request.
ADR is the message number or register number of the data being requested. In Modbus, register
addresses begin at 40001 but is interpreted as address 00.
DAT is the number of words being requested. A word is an integer consisting of 2 bytes.
The normal response from a slave is as follows:
DBC is the data byte count being returned. It must be two times the DAT number from the poll
request.
DATA is the data returned and is always a series of 2 byte integers. If 4 words were requested then
DBC would be 8 and there would be 8 data bytes or 4 data words containing the requested data.
The format of the data is 4800,N,8,1 meaning 4800 baud, no parity, and 1 stop bit.
Below is a table of currently available messages provided by the Flame-Monitor programmers, fol-
lowed by a description where necessary, EP engineering code 38 or greater and EPD engineering
code 4 or greater.
DST
FNC
ADR
HI
ADR
LO
DAT
HI
DAT
LO
CRC
LO
CRC
HI
DST
FNC
DBC
DATA….
Hi/Lo
CRC
LO
CRC
HI
MESSAGE
ADDRESS
WORD
REQUESTED
RESPONSE
VALUE
00
1-6
STATUS
83 (053H) = RUN;
202 (0CAH) = LOCKOUT
01
1
MSGN
Current message being displayed (see Table 1)
02
1
GSTAT
Defines Timer Type
03
1
TIMER
Time, Flame, Address
04
1
FLAME
Flame Signal
05
1-3
LOGSTAT
Current logic module, PURGE, PTFI, AUTO (See Table 2)
06
1
INPUTS
Input limits state
07
1
OUTPUTS
Output relays state
08
2
SYSMINS
System on minutes
10
2
BNRMINS
Burner on minutes
12
2
CYCLES
Completed Burner Cycles
14
1
LOCKOUT COUNT
Stored Lockout Count
15
1-6
LOCKOUT HISTORY
Last 6 Lockouts, first word is most current lockout
21
1-2
DEVTYP
Programmer device type, 5=EP, 6=EPD, 7=MicroM
22
1
AMPTYP
Amplifier Type; EUVS4=0C0H;
EIR1=0A0H;
ERT1, EUV1=090H;
23
24
2
FLAME SIGNAL
AVERAGES
PTFI and Auto Flame Signal Averages
35
6
Most Recent
Lockout Data
Returns complete lockout description of stored lockout history.
Includes lockout message, lockout module, @ burner hours, and @
burner cycles
