31
Battery Voltage
Min voltage
Load Sink Current
V
T
I
T
Battery Voltage
Min voltage
Load Sink Current
V
T
I
T
Diagram 4-16 Battery capacity calculation
4.8 Communication protocol
4.8.1 Introduction
M97 series programmable electronic loads work on the Modbus protocol. The data frame contains 4 parts
as follows:
Salve Address
Function Code
Data
Error
Checking(CRC)
To assure high reliability communications, the frame pitch set must be greater than 3.5 times the transient
time of a single bit byte. In other words, when the comm. rate is 9600 baud, the frame pitch time must be
set greater than 11*3.5/9600=0.004s.
M97 series programmable DC electronic loads are equipped with two way asynchronous communication,
with 1 bit fixed as the start bit, 8 data bits, and 1 stop bit. It supports Non parity check, Odd Parity check
and Even parity check. The communicationsrate is selectable at 2400, 9600, 14400, 28800, 57600,
115200 baud.
1) Setting upadditional addresses and communication parameters
The additional address is a single byte with 16 hexadecimal system data; the M97 series DC electronic
loads will only respond to the request data frame that has the same additional address.
2)Setup of the additional address
Press both
Shift+0
keys
in sequence, placing you in Main Menu mode., The DC electronic Load display
will be at
MENU CONFIG
.Press the key
Enter
to confirm. Using the
CONFIG Menu,
-up and down
▲
▼
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