Emerson Unidrive M700 - Page 122

122 SI-Ethernet User Guide
Issue: 1
7.2.6 Register addressing
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 Modbus Register Addressing Mode (S.15.013)) is
used.
To access a parameter number above 99 then the modified addressing mode must be
used (see Modbus Register Addressing Mode (S.15.013)), 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.
Table 7.5 Start register addressing
A reset is not required to activate the change, the addressing mode is effectively made
active immediately on changing.
NOTE
CT Parameter Addressing mode Protocol register
s.mm.ppp
Standard mm * 100 + ppp - 1
Modified mm * 256 + ppp - 1
Examples
16-bit 32-bit
Decimal Hex (0x) Decimal Hex (0x)
0.01.021
Standard 120 00 78 16504 40 78
Modified 276 01 14 16660 41 14
0.01.000
Standard 99 00 63 16483 40 63
Modified 255 00 FF 16639 40 FF
3.70.001
Standard 7000 1B 58 23384 5B 58
Modified N/A N/A N/A N/A
0.03.161
Standard N/A N/A N/A N/A
Modified 928 03 A0 17312 43 A0