Nidec Unidrive M200 User Manual page 57

Safety Product Mechanical
information information installation
8.6.3 MODBUS registers
The MODBUS register address range is 16 bit (65536 registers) which at the protocol level is represented by indexes 0 through 65535.
PLC registers
Modicon PLCs typically define 4 register 'files' each containing 65536 registers. Traditionally, the registers are referenced 1 through 65536 rather than
0 through 65535. The register address is therefore decremented on the master device before passing to the protocol.
File type
1 Read only bits ("coil")
2 Read / write bits ("coil")
3 Read only 16bit register
4 Read / write 16bit register
The register file type code is NOT transmitted by MODBUS and all register files can be considered to map onto a single register address space.
However, specific function codes are defined in MODBUS to support access to the "coil" registers.
All standard CT drive parameters are mapped to register file '4' and the coil function codes are not required.
CT parameter mapping
The Modbus register address is 16 bits in size, of which the upper two bits are used for data type selection leaving 14 bits to represent the parameter
address, taking into account the slave increments the address value by 1, this results in a theoretical maximum parameter address of 163.84 (limited
to 162.99 in software) when the default standard addressing mode (see Serial Mode (11.024)) is used.
To access a parameter number above 99 in any drive menu then the modified addressing mode must be used (see Serial Mode (11.024)), this will
allow access to parameter numbers up to 255 but also limit the maximum menu number to 63.
The Modbus slave device increments the register address by 1 before processing the command, this effectively prevents access to parameter
Pr 00.000 in the drive or option module.
The table below shows how the start register address is calculated for both addressing modes.
Parameter
0.mm.ppp
0.01.021
0.01.000
0.03.161
Data types
The MODBUS protocol specification defines registers as 16 bit signed
integers. All CT devices support this data size.
Refer to the section 8.6.7 Extended data types on page 59 for detail on
accessing 32 bit register data.
8.6.4 Data consistency
All CT devices support a minimum data consistency of one parameter
(16 bit or 32 bit data). Some devices support consistency for a complete
multiple register transaction.
8.6.5 Data encoding
MODBUS RTU uses a 'big-endian' representation for addresses and
data items (except the CRC, which is 'little-endian'). This means that
when a numerical quantity larger than a single byte is transmitted, the
MOST significant byte is sent first. So for example
16 - bits 0x1234 would be
32 - bits 0x12345678 would be
Unidrive M200 / M201 Control User Guide
Issue Number: 2
Electrical Getting Basic
installation started parameters
Description
Addressing mode
Standard
Modified
Standard
Modified
Standard
Modified
Standard
Modified
0x12 0x34
0x12 0x34 0x56
Running the
Optimization
motor
Protocol register
mm x 100 + ppp - 1
mm x 256 + ppp - 1
Examples
16-bit
Decimal Hex (0x)
120 00 78
276 01 14
99 00 63
255 00 FF
N/A N/A
928 03 A0
8.6.6 Function codes
The function code determines the context and format of the message
data. Bit 7 of the function code is used in the slave response to indicate
an exception.
The following function codes are supported:
Code
3 Read multiple 16 bit registers
6 Write single register
16 Write multiple 16 bit registers
23 Read and write multiple 16 bit registers
FC03 Read multiple
Read a contiguous array of registers. The slave imposes an upper limit
on the number of registers, which can be read. If this is exceeded the
slave will issue an exception code 2.
0x78
NV Media Onboard Advanced
Card PLC parameters
32-bit
Decimal
16504
16660
16483
16639
N/A
17312
Description
Diagnostics UL Listing
Hex (0x)
40 78
41 14
40 63
40 FF
N/A
43 A0
57