YASKAWA GPD 515/G5 Modbus RTU Technical Manual page 25

The normal response message contains the same slave address and function code as the
command message, indicating to the master which slave is responding and to what type of
function it is responding.
The number of data bytes is the number of data bytes returned in the response message. The
number of data bytes is actually the quantity (in the command message) times 2, since there are
two bytes of data in each register.
The data section of the response message contains 8 upper and 8 lower bits of data for each
register that has been read from the drive.
A CRC-16 value is generated from a calculation using the values of the address, function code,
number of data bytes, and register data sections of the message. The procedure for calculating a
CRC-16 value is described at the end of this chapter. How the response message is handled by
the master depends on what master is used. When the master receives the response message it
should calculate a CRC-16 value and compare it to the one in the CRC-16 field of the response
message. If these two CRC-16 values are the same the master has received the proper
response message.
Normal Response Message
SLAVE ADDRESS
FUNCTION CODE
NO. OF DATA BYTES
START-
UPPER
ING
REGISTER
LOWER
CONTENTS
UPPER
NEXT
REGISTER
CONTENTS
LOWER
UPPER
NEXT
REGISTER
CONTENTS
LOWER
UPPER
NEXT
REGISTER
CONTENTS
LOWER
LOWER
CRC-16
UPPER
02h
03h
08h
The starting register, 20h
17h
(Frequency Reference),
has a value of 1770h or
70h
6000 dec. (60.00 Hz)
The next register, 21h
17h
(Output Frequency), has
a value of 1770h or 6000
70h
dec. (60.00 Hz).
01h
The next register, 22h
(Output Current), has a
09h
value of 109h or 265 dec.
(drive rating / 8192).
00h
The next register, 23h
00h
(Control Method), has a
value of 00h or 0 dec.
(V/f Control).
38h
h
AC
The Message Format 6-5