LAN91C100 Datasheet, PDF (44/101 Pages) SMSC Corporation – FEAST™ Fast Ethernet Controller

The possible sources are:
LINK - Link Test transition
CTR_ROL - Statistics counter roll over
TXENA cleared - A fatal transmit error
occurred forcing TXENA to be cleared.
TX_SUC will be low and the specific reason
will be reflected by the bits:
TXUNRN - Transmit underrun
SQET - SQE Error
LOST CARR - Lost Carrier
LATCOL - Late Collision
16COL - 16 collisions
RX_OVRN INT Set when the receiver overruns
due to a failed memory allocation. The
RX_OVRN bit of the EPHSR will also be set, but
if a new packet is received it will be cleared. The
RX_OVRN INT bit, however, latches the overrun
condition for the purpose of being polled or
generating an interrupt, and will only be cleared
by writing the acknowledge register with the
RX_OVRN INT bit set.
ALLOC INT Set when an MMU request for TX
pages allocation is completed. This bit is the
complement of the FAILED bit in the
ALLOCATION RESULT register. The ALLOC
INT ENABLE bit should only be set following an
allocation command, and cleared upon servicing
the interrupt.
TX EMPTY INT Set if the TX FIFO goes empty,
can be used to generate a single interrupt at the
end of a sequence of packets enqueued for
transmission. This bit latches the empty
condition, and the bit will stay set until it is
specifically cleared by writing the acknowledge
register with the TX EMPTY INT bit set. If a
real time reading of the FIFO empty is desired,
the bit should be first cleared and then read.
The TX EMPTY INT ENABLE should only be set
after the following steps:
a) a packet is enqueued for transmission
b) the previous empty condition is cleared
(acknowledged)
TX INT Set when at least one packet
transmission was completed. The first packet
number to be serviced can be read from the
FIFO PORTS register. The TX INT bit is always
the logic complement of the TEMPTY bit in the
FIFO PORTS register. After servicing a packet
number, its TX INT interrupt is removed by
writing the Interrupt Acknowledge Register with
the TX INT bit set.
RCV INT Set when a receive interrupt is
generated. The first packet number to be
serviced can be read from the FIFO PORTS
register. The RCV INT bit is always the logic
complement of the REMPTY bit in the FIFO
PORTS register.
Note: If the driver uses AUTO RELEASE mode
it should enable TX EMPTY INT as well as TX
INT. TX EMPTY INT will be set when the
complete sequence of packets is transmitted.
TX INT will be set if the sequence stops due to a
fatal error on any of the packets in the
sequence.
Note: For edge triggered systems, the Interrupt
Service Routine should clear the Interrupt Mask
Register, and only enable the appropriate
interrupts after the interrupt source is serviced
(acknowledged).
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