Yokogawa JUXTA M Series Digital Limit Alarms MVTK Instrukcja Użytkownika Pobierz pdf (Strona 47)

5-1

IM 77J04J11-01E 1st Edition : 2006.08.25-00

5. MODBUS Communication

5.1 Overview

The use of MODBUS communication enables the M Series to communicate with a

PC. In this communication, you can use a PC to read/write data from/into D registers,

which are internal registers of the M Series.

A maximum of 1200 m; up to 31 slave stations

Figure 5-1 Example of Connection for MODBUS Communication

Hereafter, PCs are generically called "higher-level devices."

See Also

Chapter 6 for information on the D registers.

For the MODBUS communication of the M Series, two transmission modes are supported:

ASCII mode and RTU mode (binary system).

Table 5-1 ASCII and RTU Modes

Item ASCII Mode RTU Mode

Number of data bits 7 bits (ASCII) 8 bits (binary)

: (colon) Not necessary

Message end mark

Message start mark

CR+LF Not necessary

Message length (*1)

Error detection

2N+1 N

Data time intervals 1 second or less 24 bit time or less (*2)

Longitudinal redundancy check: LRC Cyclic redundancy check: CRC-16

*1: When the message length in the RTU mode is assumed to be "N."

*2: When the baud rate is 9600 bps, 1⫼9600⫻24 seconds or less applies.

In MODBUS communication, a higher-level device identifies each M Series with an ad-

dress number, which ranges from 01 to 99.

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 69 70

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Yokogawa JUXTA M Series Digital Limit Alarms MVTK Instrukcja Użytkownika Strona 47