Reference MVI56E-GSC/GSCXT ♦ CompactLogix or MicroLogix Platform
User Manual Enhanced Generic ASCII Serial Communication Module
Page 88 of 140 ProSoft Technology, Inc.
April 24, 2017
Port 2 Status
Port 2 receive state:
-1 = Listening for data
1 = Receiving Port Data
2 = Waiting for Backplane transfer
Port 2 receive character count
Port 2 receive block count
Port 2 transmit state:
0 = Waiting for Data to Send
1 = RTS On
2 = RTS Timeout
3 = Sending data
4 = Waiting for RTS Off
5 = RTS turned off
30 = Intercharacter Delay
31 = Intercharacter Delay
32 = Intercharacter Delay
100 = Message Delay before Transmit
101 = Message Delay before Transmit
Port 2 transmit character count
Port 2 transmit block count
Block Sequence Number (Bumped each scan by module)
The Block Sequence Number (byte 499) is an index value used to signal to the
ControlLogix processor that a new block is ready for ladder logic processing. The
ladder logic must recognize a change in this value and process the data
encapsulated in the input image.
The read block contains the data received on each port and status data for each
port. The two word-length values at bytes 1 & 2 (Port 1 Receive Length) and 251
& 252 (Port 2 Receive Length) define the number of bytes in this input image to
be processed by the ladder logic for each port. Received data for the ports are
found starting at byte 5 for Port 1and 255 for Port 2.
The ladder logic is required to handle all read data transferred from the
communication port buffers to the processor. The simple example ladder logic
assumes the received data block contains no more than 200 bytes (200 ASCII
character codes) of data for each port. Since the receive buffer for each
application port in the module can hold up to 4096 bytes (characters), the ladder
logic to handle incoming strings larger than 200 bytes is more complex than that
shown in the simple example logic.
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