Allen-Bradley 857-VPA3CG, User Manual, Page: 5 / 14

Rockwell Automation Publication 857-UM003B-EN-P - December 2017 5
857-VPA3CG Profibus DP Option Module
Data Response Message from the 857 Relay
The response is eight bytes long consisting of three fields.
The Identifier word, ID, contained in the Data Request Message, consists of 3
fields with a bit configuration is shown below.
Error codes in value field in case of response type 0111.
Request and Response Messages Examples
The master requests the measured active power from the device. The hexadecimal
byte values are:
The slave responds with the active power value.
The hexadecimal byte values are:
ID
(1)
(1) Type and number of the requested data.
IND
(2)
(2) Requested index.
VALUE
(3)
(3) Value of the requested data or error code.
Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
Response Type
(1)
(1) 0001 Read (0010 = Write).
0111 Request Rejected.
SM
(2)
(2) 0 Spontaneous bit (not used).
Parameter Number
(3)
(3) 0…2047 The number of the requested parameter.
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
0 Illegal parameter
18 Other fault
101 Unknown request type
ID
(1)
(1) 1 Request type is read.
0 00 Parameter number of active power P is 0.
IND
(2)
(2) 00 00 Index is 0.
VALUE
(3)
(3) 00 00 00 00 Dummy value.
10 00 00 00 00 00 00 00
ID
(1)
(1) 1 Response type is “Value is ready”.
000 Parameter number is 0. (Copy of request message parameter number).
IND
(2)
(2) 00 00 Index is 0 (Copy of request message index).
VALUE
(3)
(3) 00 00 OD 7A The active power is 3450 kW (ID7A
16
= 3450
10
).
10 00 00 00 00 00 0D 7A