Block Response From The Module To The Processor - ProSoft Technology MVI69-GSC CompactLogix User Manual

MVI69-GSC ♦ CompactLogix or MicroLogix Platform
Generic ASCII Serial Communication Module

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
0
Port 1 1
2
3 to 27
Port 2 28
29
30 to 54
55 to 59
The receive buffer in the module can hold up to 4096 characters. This large size permits
the buffering of a large amount of data before a transfer of the data to the controller is
required. The module buffers incoming ASCII characters in its receive buffer until one of
the user-specified termination conditions is recognized. The module will then transfer the
received terminated string to the controller.
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Description
Block Sequence Number (Bumped each scan by module) (0 to
127)
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.
Number of characters transmitted (0 to 50) from last block write
for Port 1
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.
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.
Number of characters transmitted (0 to 50) from last block write
for Port 2
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
Reserved
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