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PEB 20321
PEF 20321
IOM
-2 Interface
Data Sheet
194
2001-02-14
First Byte Reception
At the time the receiver sees the first byte, indicated by the inactive-to-active transition
of MX, MR is by definition inactive. When the receiver is ready to acknowledge the first
byte MR is activated. MR remains active until the next byte is received or an end of
message is detected (MX held inactive for two or more frame times).
Subsequent Reception
The receiver acknowledges the receipt of a valid data by the transition of MR bit from the
active to the inactive state for one frame followed by the transition to the active state in
the next frame (
Note:
Validity of the data, including the first byte, can optionally be
checked by the receiver applying a double-last-look criterion on each received data.)
The reception of data is terminated by the receipt of an end-of-transmission indication
(MX remaining inactive for two or more frame times).
End of Transmission (EOM)
–
The transmitter after receiving a successful last byte
acknowledge will indicate EOM by the transition of the MX bit from the active to inactive
state followed by the persistence of the inactive state for at least one more frame. The
contents of the monitor channel will become invalid in the same frame as the transition
of the MX bit occurs. The invalid data should be
“
11111111
”
.
The sender is then in the idle state.
Abort
–
The abort is a signal from the receiver to the transmitter indicating that data has
been missed. It is not an abort in the classical sense, which is an indication from the
transmitter that the current message should be ignored. The receiver indicates an abort
by holding MR inactive for two or more frames in response to MX going active.
Flow Control
–
The receiver can hold off the transmitter by keeping MR active until the
receiver is ready for the next byte. The transmitter will not start the next transmission
cycle until MR goes inactive.
Time-Out
–
For the cases where no device acknowledges a data, or where the
transmitter is unable to resume transmission, an optional time-out may be implemented.