ProSoft Technology MVI46-GSC - Manual (Page 44)

MVI46-GSC ♦ SLC Platform Reference
Generic Serial Communication Module
Page 44 of 78 ProSoft Technology, Inc.
December 5, 2007
Normal Data Transfer
Normal data transfer includes the transferring of data received or to be
transmitted on the ports and the status data. These data are transferred through
the M1 file using read blocks and M0 file using write blocks. Each port has a
reserved area in each of these files for the data transfer operation. In order to
coordinate the data transfer between the module and the SLC, bit 4 in the input
and output images is used. When the bits are equal, the module has control of
the M-files. When the bits are not equal, the SLC has control of the M-files. The
SLC's ladder logic must set the bits equal after interfacing with the data
exchange areas and must not use the data in the files until the bits are not equal.
The structure and function of each block is discussed below:
Read Block
These blocks of data transfer information from the module to the SLC processor.
The structure of the M1 file used to transfer this data is shown below:
Port 1
M1: File Offset Description
0 Sequence block number for this data.
1 Number of characters (0 to 256) in Port 1 receive block (words 2 to 129). If the
receive data in the module is larger than 256 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 256 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.
2 to 129 Port 1 data received (up to 128 words or 256 bytes)
Port 2
M1: File Offset Description
130 Number of characters (0 to 256) in Port 2 receive block (words 2 to 129). If the
receive data in the module is larger than 256 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 256 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.
131 to 258 Port 2 data received (up to 128 words or 256 bytes)
259 Reserved
Module Status
M1: File Offset Description
260 Program cycle counter
261 to 262 Product name as ASCII string
263 to 264 Revision level as ASCII string
265 to 266 Operating system level as ASCII string
267 to 268 Run number as ASCII string
269 Number of blocks transferred from module to processor