212-M-V2.1
Communications 35
Except for broadcast messages, when a master device sends a query to a
slave device it expects a normal response. One of four possible events can
occur from the master's query:
1. If the slave device receives the query without a communication
error, and can handle the query normally, it returns a normal
response.
2. If the slave does not receive the query due to a communication
error, no response is returned. The master program has to
process a timeout condition for the query.
3. If the slave receives the query, but detects a communications
error (parity or CRC), no response is returned. The master
program has to process a timeout condition for the query.
4. If the slave receives the query without a communication error,
but cannot handle it (for example, if the request is to read a
nonexistent register), the slave will return an exception
response informing the master of the nature of the error.
4.3.3 Bus Address
The bus address of the Model 212 is programmable in range between 1 to
247.
Some addresses are reserved according to PI-MBUS-300 and have a
special meaning:
0 Broadcast, no response
247...255 Reserved
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