7-12
PQM Power Quality Meter
GE Power Management
7.2 MODBUS FUNCTIONS
7 MODBUS COMMUNICATIONS
7
7.2.10 FUNCTION CODE 16 - BROADCAST COMMAND
In applications where multiple devices are daisy chained, it may be necessary to synchronize the clocks (date
and/or time) in all the devices by sending one command. The broadcast command allows such synchronization
as shown in an example below. The PQM will recognize a packet as being a broadcast command if the SLAVE
ADDRESS is transmitted as 0.
MESSAGE FORMAT AND EXAMPLE:
Send broadcast command to the PQM to store 1:27:10.015 pm, October 29, 1997.
The PQM allows the date and time to be stored separately. In other word, a broadcast command can be sent to
store just date or time.
Table 7–9: PACKET FORMAT FOR FUNCTION CODE 16 BROADCAST COMMAND
MASTER TRANSMISSION
BYTES
EXAMPLE
DESCRIPTION
SLAVE ADDRESS
1
11
message for slave 17
FUNCTION CODE
1
10
store multiple setpoints
DATA STARTING ADDRESS
2
00 F0
start at address 00F0
NUMBER OF SETPOINTS
2
00 04
4 setpoints = 8 bytes total
BYTE COUNT
1
08
8 bytes of data
DATA 1
2
0D 1B
hours (24 hour format), minutes
DATA 2
2
27 1F
milliseconds
DATA 3
2
0A 1D
month, day
DATA 4
2
07 CD
year (four digits, i.e. 1997)
CRC
2
9D 8D
CRC error code
SLAVE RESPONSE
BYTES
EXAMPLE
DESCRIPTION
Slave does not respond back to the master.
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