Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 63)

4–15 Planning an Application
Publication 2706-817
A MessageView terminal with a RIO daughterboard (Catalog Nos.
2706-M1D1, -M1N1 or -M1F1) and firmware that supports a Slave
Port can act as a master device with up to 126 slave devices.
Note: A MessageView 421D terminal without a daughterboard can
be used as a slave device. A list of slave devices is given on Page
5–6.
An example of a master terminal setup with four slaves
MessageView Terminal
RS-232
RIO
PLC5
RS-232
RS-485
RS-485
Black
Box
Black
Box
Black
Box
Black
Box
Black
Box
Slave
Slave
Slave
Slave
MessageView Terminal slave buffers
Each slave device is addressed individually. The MessageView
terminal has 14 buffers that store messages that are monitored,
updated, and continuously displayed by the slave(s). Each slave on
the network has its own node address. Each message is directed to a
specific slave to be displayed on a specific line.
The MessageView Terminal buffer system works as follows:
1. Message 1, sent to the slave at node 6 slated for line 1, is stored in
one of the buffers and displayed immediately by the slave.
2. Message 2, sent to the slave at node 2 slated for line 1, is stored in
another buffer and displayed by the second slave.
3. Message 3, sent to the slave at node 6 slated for line 2, is stored in
a third buffer and displayed concurrently with Message 1.
4. Message 4, sent to the slave at node 6 slated for line 1, overwrites
the message in the first buffer and is slaved at once.
5. If all the buffers are full, and if no buffer has a message for the
slave at node 6 line 4, a new message for the slave at node 6 line
4 overwrites the message in the oldest node 6 buffer. If none of
the buffers has a message for node 6, then the oldest buffer is
overwritten, no matter which node it was addressed to.
Slaving