ProSoft Technology MVI71-GEC - Manual (Page 50)

Reference MVI71-GEC ♦ PLC 5 Platform
User Manual Generic ASCII Ethernet Communication Module
Page 50 of 86 ProSoft Technology, Inc.
May 11, 2011
Read Block
These blocks of data transfer information from the module to the PLC processor.
When data is received on one of the servers, a data block is built. The structure
of this block type is shown in the following table.
Word
Offset Description
0 Block Sequence Number (Bumped each scan by module)
Received
Data
1 Server Number for data received. If the word contains a value of -1 or -2,
no receive data is present and the block contains status data. If the word
contains a value from 0 to 4, the block contains data from one of the
servers in the module.
2 Number of characters (0 to 110) in receive block (3 to 57). If the receive
data in the module is larger than 110 bytes, multiple blocks will be
transferred. Any block with a value of -1 in this field represents the first or
continuation block and the block contains 110 bytes of data. The last block
of data will contain a positive number in this field that represents the
number of characters in the last block.
3 to 57 110 bytes of data received for specified server.
58 Server 0 State
59 Server 1 State
60 Server 2 State
61 Server 3 State
62 Server 4 State
63 Number of characters processed from last write block.
Word Offset 0 contains an index value used to signal to the PLC processor that a
new block is ready for processing. The ladder logic must recognize a change in
this value and process the data encapsulated. If data is available for a server, a
block containing data received is passed to the processor.
Word Offset 1 contains the server index (0 to 4) that is sending the data to the
processor.
Word Offset 2 contains a value that determines the number of characters (or
bytes) in the data area of the block. If the server receives a message longer than
110 bytes, it must send the received message in multiple blocks to the processor.
In this case, the byte count field of the block will be set to -1 for each block where
more than 110 characters are being sent by the server. Each block with a byte
count field of -1 contains 110 bytes of data. The data set is located in the block
starting at word offset 3. When the last block of data to send by the server is less
than or equal to 110 bytes, the byte count field will be set to a number from 1 to
110. This signifies to the processor that this is the last block. The ladder logic
must handle data received on each server enabled in the module.
If no data is available, the module will page one of the two status data images to
the processor. If word 1 of the BTR block is set to -1, the data for the first three
servers, the product and block transfer data is sent in the block. The format of
this block is as follows: