7–14 PQM POWER QUALITY METER – INSTRUCTION MANUAL
MODBUS FUNCTIONS CHAPTER 7: MODBUS COMMUNICATIONS
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 00
broadcast command
(address = 0)
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.
Courtesy of NationalSwitchgear.com
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