Number Of Tokens Passed; Number Of Tokens Heard; Number Of Passes Through No Successor 8; Number Of Who Follows - Motorola MC68824 User Manual

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If the threshold value has been exceeded, the status bit threshold counter exceeded (TCE) in
interrupt status word 1 is set. If enabled by the TCE bit in interrupt mask word 1, an interrupt is
also generated. A threshold value of zero disables the interrupt mechanism, however the counters
are still incremented. The threshold mechanism allows software to map the 16-bit counters into
larger counters (32 bits), or to be notified if a large number of errors occurs. Counters are not
automatically cleared when the threshold value is reached. The collection of two ofthese statistics
which are number of tokens passed and number of tokens heard may be disabled using the SET
MODE 1 command (see 3.3.1 SET MODE 1 Command).These counters are described in the fol-
lowing paragraphs.
2.2.13.1 NUMBER OF TOKENS PASSED. This statistic is the number of tokens that have been
passed by this station. The counter is incremented when the TBC thinks it successfully passed
the token to its successor in the ring. In normal operation, this is equal to the number of tokens
passed to the TBC. This statistic enables software to calculate the average token rotation time.
The collection of this statistic may be disabled using the SET MODE 1 command.
2.2.13.2 NUMBER OF TOKENS HEARD. This statistic represents the number of tokens this station
has heard on the network with DA not equal to TS and SA not equal to TS, that is the number
of tokens that have gone by. This counter, along with the tokens passed counter, the
:':0
ken skipped
and token passed status bits in interrupt status word 0, may be used to estimate the number of
stations in the logical ring. The collection of this statistic may be disabled using the SET MODE
1 command.
2.2.13.3 NUMBER OF PASSES THROUGH NO SUCCESSOR 8. This statistic indicates the number
of times this station has gone through the no successor 8 arc in the state machine. This happens
when the TBC fails to pass the token and does not succeed in finding a new successor station.
The counter is incremented only if the TBC thinks it is not the only active station in the network.
A significantly large value in this counter may indicate a IIfaulty" transmitter condition in this
station.
2.2.13.4 NUMBER OF WHO FOLLOWS. This statistic is the number of times this station has had
to look for a new next station to pass the token to. This frame is sent as part of the TBC's effort
to pass the token to its former successor's successor if the original successor station does not
respond to the token. This counter is incremented by two every time a failure occurs.
2.2.13.5 NUMBER OF TOKEN PASS FAILED. This statistic indicates the number of token pass
failed transitions when pass state is equal to pass token. Upon failing to pass the token, the TBC
tries to send a second token (pass state equals repeat pass token). If this effort fails too, this
counter is not incremented again; but the TBC will then send a who follows frame and the who
follows query counter will be incremented.
2.2.13.6 NUMBER OF FRAMES TOO LONG (>8K BYTES). This statistic is the number of received
frames that are too long (>8K bytes, an IEEE 802.4 parameter). If frames are longer than 8K, they
may be accepted if the appropriate bit is set in the receive frame status error mask (see 4.1.1.2
RECEIVE STATUS WORD for a description) in the initialization table.
2.2.13.7 NUMBER OF NO FD/BD ERRORS. This statistic counts the number of frames that were
not received because there were not enough frame descriptors or there were not enough buffers.
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MC68824 USER'S MANUAL