ProSoft Technology MVI69-GSC - Manual (Page 78)

Reference MVI69-GSC ♦ CompactLogix or MicroLogix Platform
User Manual Generic ASCII Serial Communication Module
Page 78 of 102 ProSoft Technology, Inc.
September 24, 2010
Block Response from the Module to the Processor
These blocks transfer information from the module to the processor. The
structure of the input image used to transfer these data is shown below. The
Block Sequence Number (byte 0) is an index value used to signal to the
processor that a new block is ready for processing. The ladder logic must
recognize a change in this value and process the data encapsulated in the input
image. The block contains the data received on each port and status data. The
two byte values in bytes 1 (port 1 receive length), and 28 (port 2 receive length),
hold the number of characters received on each port to be processed by the
ladder logic. ASCII character code data received on the ports are found starting
at byte 3 and 30 for Port 1 and 2, respectively. The simpler version of the
example ladder logic assumes the number of ASCII characters received on each
port is less than or equal to fifty characters (25 words per port, times 2 characters
per word).
Word Offset Description
0 Block Sequence Number (Bumped each scan by module) (0 to
127)
Port 1 1 Number of characters (0 to 50) in Port 1 receive block (3 to 27). If
the string received on the port is larger than 50 characters,
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 50 characters of ASCII code data. The last block of data
will contain a positive number in this field that represents the
number of characters in the last block. Status data will be returned
in words 3 to 27 if this word contains a value of 0.
2 Number of characters transmitted (0 to 50) from last block write
for Port 1
3 to 27 Port 1 data received (up to 50 ASCII character codes of data). If
the number of characters received for the port is 0, status data will
be returned in this area.
Port 2 28 Number of characters (0 to 50) in Port 2 receive block (30 to 54).
If the string received on the port is larger than 50 bytes, multiple
blocks will be transferred. Any block with a value of -1 in this field
represents the first of continuation block and the block contains 50
characters of ASCII code data. The last block of data will contain
a positive number in this field that represents the number of
characters in the last block. Status data will be returned in words
30 to 54 if this word contains a value of 0.
29 Number of characters transmitted (0 to 50) from last block write
for Port 2
30 to 54 Port 2 data received (up to 50 ASCII character codes of data). If
the number of characters received for the port is 0, status data will
be returned in this area
55 to 59 Reserved