Rockwell Automation 1203-SM1 SLC to SCANport Communication Module - Manual (Page 37)

4–9 Using Enhanced Mode
Publication 1203–5.9 –– October 1996
The eight unique message buffers in the M0 file can contain a
message for any of the three SCANport channels. You can select
which message buffer is to be used for each channel with the
corresponding MSG ID bits. This lets a message be written into a
buffer only once and used as many times as needed.
To transmit a message, the MSG ID bits are set to select the desired
buffer and a channel’s Message Enable bit is set to 1. When the
message status bits indicate the message is done, the response can be
read from the M1 message buffer area for the corresponding
SCANport channel used. When the Message Enable bit is
subsequently cleared to 0, the DONE status bit will be reset and the
READY bit set to allow for another message sequence.
The definition for the channel command output image is as follows:
Channel 2 Command
Bit
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Word 0
Word 1
Channel 1 Command
Channel 3 Command
Not Used MSG ID Not Used MSG ID
Not Used MSG ID Reserved
DE
2
ME
2
DE
1
ME
1
DE
3
ME
3
These bits have the following definitions:
This: Represents the:
DE1
DE2
DE3
SCANport Channel 1, 2, or 3 Data Enable bit. While low (0),
the channel is not transferring I/O data (including datalink data)
between the connected SCANport device. When high (1), the
channel becomes active to the SCANport device and transfers
the appropriate I/O data. When cleared to low (0), the channel
disconnects from the SCANport device, which usually causes
the connected SCANport device to fault.
ME1
ME2
ME3
SCANport Channel 1, 2, or 3 Message Enable bit. When set
high (1), the message selected by the Message ID field is
transmitted through the appropriate channel to the SCANport
device. This bit should be held high during the duration of the
request until the status DONE bit is asserted (1). The clearing
(0) of this bit clears the DONE status and returns the message
status to the READY state.
MSG
ID
Message Identifier field. This field allows for the selection of
one of the eight message buffers in the M0 file area for each
channel. Multiple channels can use the same message ID buffer
simultaneously.