Chapter 8 Communication Function
8-65
8.3 Modbus Protocol Communication
8.3.1 Introduction
MK80S built-in communication supports Modbus, the Modicon product’s communication protocol. It supports ASCII mode, using
ASCII data and RTU mode using Hex data. Function code used in Modbus is supported by instruction and especially function code
01, 02, 03, 04, 05, 06, 15, and 16. Refer to "Modicon Modbus Protocol Reference
Guide"(
http://www.modicon.com/techpubs/toc7.html).
8.3.2 Basic Specification
1)
ASCII mode
(1)
It communicates, using ASCII data.
(2)
Each frame uses ': (colon : H3A)', for header, CRLF (Carriage Return-Line Feed : H0D H0A), for tail.
(3)
It allows Max. 1 second interval between characters.
(4)
It checks errors, using LRC.
(5)
Frame structure (ASCII data)
Item
Header
Address
Function code
Data
LRC
Tail
(CR LF)
Size
1 byte
2 bytes
2 bytes
n bytes
2 bytes
2 bytes
2)
RTU mode
(1)
It communicates, using hex data.
(2)
There's no header and tail. It starts with address and finishes frame with CRC.
(3)
It has at least 3.5 character times between two frames.
(4)
It ignores the current frame when 1.5 character times elapse between characters.
(5)
It checks errors, using 16 bit CRC.
(6)
Frame structure (hex data).
Item
Address
Function code
Data
CRC
Size
1 byte
1 bytes
n bytes
2 bytes
1)
The size constituting 1 letter is 1 character. So 1 character is 8 bits that is 1 byte.
2)
1 character time means the time lapsed for sending 1 character.
Ex) Calculation of 1 character time at 1200 bps.
1200 bps means that it takes 1 sec to send 1200 bits. To send 1 bit, 1 sec/1200 bits = 0.83 ms. Therefore 1
character time is 0.83ms * 8 bits = 6.64ms.
3)
584, 984 A/B/X executes frame division, using intervals of more than 1 sec without LRC in processing internally.
REMARK
Содержание MASTER-K80S
Страница 27: ...Chapter 4 Names of Parts 4 4 1 3 30 points base unit 4 1 4 40 points base unit 4 1 5 60 points base unit...
Страница 66: ...Chapter 6 Input and Output Modules 6 3 30 point base unit 4 40 point base unit DC24V DC24V DC24V...
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Страница 206: ...Chapter 8 Communication Function 8 63 You can see the frame list which is designated Click OK button...
