Motorola MC68838 User Manual page 30

The SENT_COUNT is not cleared (stripping continues) if a duplicate token is
received (i.e., a token received while transmitting).
When this bit is one, the MAC transmitter internally creates and transmits one
special void frame after leaving the TX_Data state (i.e., just before it would
normally release the token). This MAC chip always creates and transmits a
special void frame with the following characteristics:
FC = 48-bit addressed void frame
DA = my long address register
SA = my long address register
Zero INFO bytes
FCS = valid CRC
EFS = TRRR.
When RING_OPERATIONAL is zero, this bit is ignored by the MAC chip.
TXPARITY_ON—Transmit Parity Check On
0 = The TPRlTY input in the TPATHx bus is ignored.
1 = TPATHx and TPRITY together must have odd parity (i.e., an odd number of the
nine lines must be high), or the MAC aborts the transmission of this frame and
asserts TABORT.
REPEAT_ONLY—Repeat Only
The transmitter cannot capture the token.
0 = The transmitter operates normally.
1 = The MAC will not start sending any more frames from the FSI, although it can
finish any frames it has started to send as well as sending any frames internally
generated by the MAC (i.e., claim, beacon, and void frames). Specifically, the
conditions USABLE_TOKEN and ANOTHER_FRAME are always zero; thus, the
transmitter cannot capture a token. If it has the token, it cannot send any more
frames although it can finish sending the frame it is currently sending (plus any
associated token). The transmitter cannot start sending frames whose
TOKEN_TYPE field in the packet request header allows the frame to be sent
without a token. When REPEAT_ONLY = 1 and RING_PURGE = 1, the MAC will
still capture the token, send two special void frames, and then release the same
kind of token.
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