Note: Words 23 ... 26 contain the active station bitmaps. An active station is any one that has sent packets of data over the network. Note

Note: Words 31 ... 34 contain the global data present table bitmaps. Each time a station passes a
token, it also passes the global data, even if there are zero bytes of global data. When one
station sees another pass the token with global data, it sets its bit in its table for that other
station. The bit remains set until the station reads the global data from that other station, after
which the bit is cleared. A second read of global data indicates that no global data is present.
Note: In screen 2 of the MBPSTAT program, the number of global data words present is
indicated under the station number. If this field is filled with spaces, then MBPSTAT has
requested the global data from a second time before the other station passed the token.
Note: The LO bytes of words 35 ... 37 indicate the use of the internal receive buffers within the
peer processor.
http://www.modicon.com/techpubs/diag7.html (15 of 16) [1/11/2000 10:43:11 PM]

http://www.modicon.com/techpubs/diag7.html (16 of 16) [1/11/2000 10:43:11 PM]

Chapter 4
Exception Responses
V 
Exception Responses
V 
Exception Codes
4.1 Exception Responses
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:
V If the slave device receives the query without a communication error, and can handle the
query normally, it returns a normal response.
V If the slave does not receive the query due to a communication error, no response is returned.
The master program will eventually process a timeout condition for the query.
V If the slave receives the query, but detects a communication error (parity, LRC, or CRC), no
response is returned. The master program will eventually process a timeout condition for the
query.
V If the slave receives the query without a communication error, but cannot handle it (for
example, if the request is to read a nonexistent coil or register), the slave will return an
exception response informing the master of the nature of the error.
The exception response message has two fields that differentiate it from a normal response:

tải về 0.61 Mb.

Chia sẻ với bạn bè của bạn: