Appendix A - Modbus Interface; A.1.Modbus Interface Register / Bit Map; Register Map; Modbus Transmission Mode - Hitachi HX-RIO3 Series User Manual

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A. APPENDIX A - MODBUS INTERFACE

A.1.MODBUS Interface Register / Bit Map

A.1.1 Register Map
Start Address
0x0000 ~
0x0800 ~
0x1000 ~
0x1020 ~
0x1100 ~
0x2000 ~
* The special register map must be accessed by read/write of every each address (one address).
Bit Map
•
Start Address
0x0000 ~
0x0800 ~
A.2. MODBUS Transmission Mode
Two different serial transmission modes are defined: The RTU mode and the ASCII mode. It defines the
bit contents of message fields transmitted serially on the line. It determines how information is packed into
the message fields and decoded.
A.2.1. RTU Transmission Mode
When devices communicate on a MODBUS serial line using the RTU (Remote Terminal Unit) mode, each
8–bit byte in a message contains two 4–bit hexadecimal characters. The main advantage of this mode is
that its greater character density allows better data throughput than ASCII mode for the same baudrate.
Each message must be transmitted in a continuous stream of characters.
Start Address
≥ 3.5 chars
1 char
Read/Write Description
Read Process input image registers (Real Input Register)
Read/Write Process output image registers (Real Output Register)
Read Adapter Identification special registers.
Read/Write Adapter Watchdog, other time special register.
Read/Write Adapter Information special registers.
Read/Write Expansion Slot Information special registers.
Read/Write Description
Process input image bits
All input registers area is addressable by bit address.
Read
Size of input image bit is size of input image register *
16.
Process output image bits
All output registers area is addressable by bit address.
Read/Write
Size of output image bit is size of output image register *
16.
Function
1 char
Data
Up to 252 chars
HX-RIO3 Series
Func.
Code
4, 23
3, 16, 23
3, 4, 23
3, 4, 6, 16,
23
3, 4, 6, 16,
23
3, 4, 6, 16,
23
Func.
Code
2
1, 5, 15
CRC Check End
≥ 3.5 chars
2 chars