ProSoft Technology MVI56E-MNETR - Manual (Page 112)

MVI56E-MNETR ♦ ControlLogix Platform Reference
Modbus TCP/IP Interface Module with Reduced Data Block User Manual
Page 112 of 153
ProSoft Technology, Inc.
August 31, 2009
In formatted pass-through mode, the module processes the received write
request and generates a special block dependent on the function received. There
are two modes of operation when the formatted pass-through mode is selected. If
code 2 is utilized (no swap), the data received in the message is presented in the
order received by the module. If code 3 is utilized (swap mode), the bytes in the
data area of the message will be swapped. This selection is applied to all
received write requests. The block identification code used with the request
depends on the Modbus function requested. Block 9956 passes word type data
for functions 6 and 16. Block 9957 passes a floating-point message for functions
6 and 16. Block 9958 is utilized when Modbus function 5 data is received. Block
9959 is employed when function 15 is recognized. Block 9960 is used for
function 22 and Block 9961 is used for function 23 requests. Block 9970 is
utilized for function 99. The following tables describe the format for the read
blocks.
Formatted
Formatted Pass-Through Command Blocks (Read Block)
Offset Description Length
0 9956, 9957, 9958, 9960 or 9961 1
1 Number of word registers in Modbus data set 1
2 Starting address for Modbus data set 1
3 to 40 Modbus data set 38
41 9956, 9957, 9958, 9960 or 9961 1
Formatted Pass-Through Command Blocks (Read Block)
Offset Description Length
0 9959 1
1 Number of word registers in Modbus data set 1
2 Starting word address for Modbus data set 1
3 to 21 Modbus data set 19
22 to 40 Bit mask to use with the data set. Each bit to be considered
with the data set will have a value of 1 in the mask. Bits to
ignore in the data set will have a value of 0 in the mask. 19
41 9959 1
Formatted Pass-Through Command Blocks (Read Block)
Offset Description Length
0 9970 1
1 1 1
2 0 1
3 to 40 Spare data area 38
41 9996 1
The ladder logic should copy and parse the received message and control the
processor as expected by the master device. The processor must respond to the
formatted pass-through control blocks with a write block. The following tables
describe the format of the write blocks.