Yokogawa 212 Heat Calculator - Manual (Page 38)

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
36 Communications