MVI46-GEC
♦
SLC Platform
Reference
Generic ASCII Ethernet Interface Module
Page 48 of 78
ProSoft Technology, Inc.
April 30, 2008
Word
Offset
Description
Module
Status
102 to 234
This data area contains the status data block. Each block transferred to
the processor contains this set of information.
235 to 246
Reserved for future use.
247
Value for designated Server or Client number during writing process. (0
to 4) for Servers (10 to 14) for clients.
248
Number of characters processed from last write block (0 to 400).
249
Block Sequence Number (Bumped each scan by module)
The Block Sequence Number (word 249) is an index value used to signal to the
SLC processor that a new block is ready for processing along with the first bit of
word 0 in the Input and word 0 in the Output image of the module.
When the two bits are equal (both on or both off), the module has control of
the M-files.
When the two bits are not equal, the SLC has control of the M-files.
This coordination insures that the data in the files will not be changed by the one
of the processors when it is being read or written by the other processor. The
ladder logic must recognize a change in this value of the I/O bits and process the
encapsulated data.
If data is available for a Server, a block containing received data and the
complete status data area is passed to the processor. The value at word offset 0
in the block contains the server index (0 to 4) that is sending the data to the
processor. If word offset 0 is set to a value of -1, no data has been received on
any connected server that must be transferred to the processor.
If data is available for a Client, a block containing received data and the complete
status data area is passed to the processor. The value at word offset 0 in the
block contains the Client index (10 to 14) that is sending the data to the
processor. If word 0 is set to a value of -1, no data has been received on any
connected Client that must be transferred to the processor
Word 1 determines the number of bytes in the data area of the block. This word
only has significance if word 0 of the block is set to a valid server index value (0
to 4) or valid Client index value (10 to 14).
Multiple Read Blocks
If the server receives a message longer than 200 bytes (100 words), 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 200
characters are being sent by the server. Each block with a byte count field of -1
contains 200 bytes (100 words) of data. The data set is located in the block
starting at word offset 2. When the last block of data to send by the server is less
than or equal to 200 bytes (100 words), the byte count field will be set to a
number from 1 to 200. This indicates to the processor that this is the last block.
The ladder logic must handle data received on each server enabled in the
module.
