Protocol Function - Emerson EV1000-2S0004G User Manual

Address Parameter Reply bytes Register content
0x01 0x03 0x02
In ASCII mode, the frame head is "0x3A", and default frame
tail is "0x0D" or "0x0A". The frame tail can also be configured
by users. Except frame head and tail, other bytes will be sent
as two ASCII characters, first sending higher nibble and then
lower nibble. The data have 7 bits. "A"~"F" corresponds to
the ASCII code of respective capital letter. LRC check is
used. LRC checksum is calculated by adding all the
successive 8-bit bytes of the message except the head and
tail, discarding any carriers, and then complementing the
result.
Example of Modbus data frame in ASCII mode:
The command frame of writing "4000 (0xFA0) " into Register
002 of Drive No. 1 is shown in the table below:
LRC checksum=the complement of
(01+06+00+02+0x0F+0xA0) = 0x48
Frame Function
Address
head code
Code : 0 1 0 6
ASCII 3A 30 31 30 36 30 30 30 32 30 46 41 30 34 38 0D 0A
Different respond delay time can be set through drive's
parameters to adapt to different needs. For RTU mode, the
respond delay time should be no less than 3.5 bytes interval,
and for ASCII mode, no less than 1ms.

4. Protocol Function

The main functions of Modbus is to read and write
parameters. The Modbus protocol supports the following
function code:
Function code
Read drive's parameter and operation status
0x03
parameters
Modify single drive's parameter or control
0x06
parameters. Not save them upon power-off.
0x08 Serial line diagnosis
Modify several drives' parameter or control
0x10
parameters. Not save them upon power-off.
Modify single drive's parameter or control
0x41
parameters. Saving them upon power-off.
0x42 Parameter management
All drive's parameters, control and status parameters are
mapped to Modbus R/W Register. The R/W properties of the
parameters and their setting ranges are specified in the user
manual. The group number of the drive's parameter maps to
the most significant byte of the register address, and the
index number of the parameter in the group maps to the
least significant byte. The control and status parameters of
the drive are virtually taken as parameter group. The
relationship of group number of the parameters and the most
significant byte of register address is listed below:
F0 group: 0x00; F1 group: 0x01:
Checksum
0x13 0x88 0xB5 0x12
Register Check
Content
Address sum
0 0 0 2 0 F A 0 4 8 CR LF
Function
EV1000 Series General Purpose Variable Speed Drive User Manual
Appendix 2 Communication Protocol
F2 group: 0x02; F3 group: 0x03;
F4 group: 0x04; F5 group: 0x05;
F6group: 0x06; F7 group: 0x07;
F8 group: 0x08; F9 group: 0x09;
FA group: 0x0A; Fb group: 0x0B;
FC group: 0x0C; Fd group: 0x0D;
FE group: 0x0E; FF group: 0x0F;
FH group: 0x10; FL group: 0x11;
Fn group: 0x12; FP group: 0x13;
FU group: 0x14;
Drive control parameter group: 0x32;
Drive status parameter group: 0x33.
E.g. the register address of F3.02: 0x302, register address
of FF.01: 0xF01.
The above shows the format of the frame. Now we will
introduce the Modbus function code and data unit for
different function in details, which is called protocol data unit
Frame
for simplicity. Also MSB stands for the most significant byte
tail
and LSB stands for the least significant byte for the same
reason. The description below is data format in RTU mode.
The length of data unit in ASCII mode should be doubled.
Protocol data unit format of reading parameters:
Request format:
Protocol data unit
Function code
Initial register address
Register number
Response format:
Protocol data unit
Function code
Number of bytes read out
Contents
If the operation fails, error code and exception code forming
the protocol data unit will be replied. The error code is
(Parameter+0x80) . The exception code denotes reason of
the error; see the table below.
Table 1 Exception Code Meaning
Exception
code
0x1 Invalid parameter.
0x2 Invalid register address.
0x3 Data error, exceeding upper or lower limit
Drive operation failure, including invalid data, although
0x4
within upper and lower limit.
Valid command, processing, mainly used in storing data
0x5
into involatile memory.
Drive busy, please try later. Mainly used in storing data
0x6
into involatile memory.
Information frame error, including data length or
0x18
checksum error.
0x20 Parameter cannot be modified
0x22 Parameter protected by password.
Data length (bytes) Range
1
2 0x0000~0xFFFF
2 0x0001~0x0004
Data length (bytes)
1 0x03
1 2*Register Qty.
2*Register Qty.
Meaning
75
0x03
Range