ProSoft Technology MVI71-MNET - Manual (Page 62)

MVI71-MNET ♦ PLC Platform Reference
Modbus TCP/IP Interface Module User Manual
Page 62 of 109
ProSoft Technology, Inc.
June 23, 2009
The module uses the following block numbers:
Block Range Descriptions
-1 Null block
0 Null block
1 to 84 Read or write data
1000 to 1083 Output Initialization Blocks
2000 Event Command Block
5001 to 5006 Command Control
9956 Formatted pass-through block from function 6 or 16 with word data.
9957 Formatted pass-through block from function 6 or 16 with floating-point data.
9958 Formatted pass-through block from function 5.
9959 Formatted pass-through block from function 15.
9960 Formatted pass-through block from function 22.
9961 Formatted pass-through block from function 23.
9970 Function 99 indication block.
9996 Unformatted Pass-through block with raw Modbus message.
9998 Warm-boot control block
9999 Cold-boot control block
These block identification codes can be broken down into a few groups: Normal
data transfer blocks (-1 to 84), Initialization blocks (1000 to 1083), Command
control blocks (2000, 5000 to 5006, 9998 and 9999) and pass-through function
blocks (9956 to 9961, 9970 and 9996). Each of these groups of blocks are
discussed in the following topics:
Normal Data Transfer
Normal data transfer includes the paging of the user data found in the module’s
internal database in registers 0 to 4999 and the status data. These data are
transferred through read (BTR) and write (BTW) blocks. The following topics
describe the function and structure of each block.
Read Block
These blocks of data transfer information from the module to the PLC processor.
The following table describes the structure of the input image.
Offset Description Length
0 Read Block ID 1
1 Write Block ID 1
2 to 61 Read Data 60
62 to 63 Spare 2
The Read Block ID is an index value used to determine the location of where the
data will be placed in the PLC processor controller tag array of module read data.
Each transfer can move up to 60 words (block offsets 2 to 61) of data.