Transmission Principle For Data Source Main And Batch Counter / Main Counter And Totalizer; Modbus Protocol; Master - Slave Principle; Transmission Principles - Trumeter 898X Serie Manual De Instrucciones

4.1.2 Transmission principle for data source main and batch counter / main counter and
totalizer
Transmission: main and secondary counter
Address 1 Space
2 bytes 1 byte
Address 2 Space
2 bytes 1 byte
Example for data source main and batch counter:
15 [SPACE]
3135 20
hex hex
16 [SPACE]
3136 20
hex hex
Bold:
Normal:

5 MODBUS protocol

The MODBUS data transmission in binary form takes place in the RTU (Remote Terminal Unit) operating
mode, via the serial interface (RS485). The protocol is implemented following the specifications (MODBUS
Application Protocol Specification V1.1b and MODBUS over Serial Line – Specification and Implementation
Guide V1.02.) of the MODBUS Organization.

5.1 Master - Slave principle

The protocol operates according to the Master-Slave principle. A Master can communicate with one or
several Slaves. Only the slave explicitly addressed by the Master is allowed to send data back to the Master.
Response from
address X

5.2 Transmission principles

The protocol has two different transmission principles.
Unicast mode
In Unicast mode, the Master addresses a determined Slave. The Slave processes the message and sends an
answer back to the Master. Every Slave has a univocal address in the address range from 1 to 247. The
transmission principle always consists in a request from the Master and the subsequent response from the
Slave. If the Master does not receive a response within a defined period of time (Timeout), the Master can
assume that errors occurred during the transmission.
Broadcast mode
In Broadcast mode, the Master sends a write instruction (request) to all Slave devices, which do not generate
any response. Broadcast addressing uses address 0.
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Text Space
4 bytes 1 byte
Text Space
5 bytes 1 byte
MAIN
4D41 494E
hex
BATCH [SPACE]
42 4154 4348
hex
ASCII
HEX value
Message to
address X
Slave
Address X
Sign Data value
1 byte 6 or 7 bytes
Sign Data value
1 byte 6 or 7 bytes
[SPACE] +
20 2B
hex hex
+
20 2B
hex hex
Master
Slave
Address Y
Carriage Return Line Feed
1 byte
Carriage Return Line Feed
1 byte
000259
3030 3032 3539
hex
999999
3939 3939 3939
hex
Bus RS485
Slave
Address Z
1 byte
1 byte
[CR] [LF]
0D 0A
hex hex
[CR] [LF]
0D 0A
hex hex