IA80C152 Datasheet, PDF (21/32 Pages) InnovASIC, Inc – UNIVERSAL COMMUNICATIONS CONTROLLER

Page 21 of 32
IA80C152
Preliminary Data Sheet
UNIVERSAL COMMUNICATIONS CONTROLLER
7
6
5
LNI
NOACK
UR
4
TCDT
3
TDN
2
TFNF
1
TEN
0
DMA
DMA - If this bit is set it indicates that the DMA channels are used to service the RFIFO and TFIFO and that GSC
interrupts occur on TDN and RDN. If set it also enables UR to become set. If this bit is cleared it indicates that the
GSC is operating in normal mode and interrupts occur on TFNF and RFNE.
TEN - When TEN is set it will cause TDN, UR, TCDT and NOACK to be reset and the TFIFO to be cleared. The
transmitter will clear TEN after a successful transmission, a collision during data, CRC or end flag. The user sets the
bit and the user of the GSC can clear the bit. If the bit is cleared during a transmission the transmit pin goes to a high
level. This is the method used to send an abort character in SDLC. DEN is also forced to a high level. An end of
transmission occurs whenever the TFIFO is emptied.
TFNF - If this bit is a 1 TFIFO is not full and new data may be written to it.
TDN - The GSC sets this bit to indicate that a frame transmission completed successfully. If HABEN is set, TDN
will not be set until the end of the IFS so that the acknowledge can be checked. TDN will not be set if an
acknowledge is expected but not received. An acknowledge will not be expected after a broadcast or a multi-cast
packet.
TCDT - The GSC sets this bit to indicate that the transmission stopped due to a collision. The bit is set by a collision
occurring during the data, the CRC or if there are more than 8 collisions.
UR - The GSC sets this bit to indicate that in DMA mode the last bit was shifted out of the transmit register and that
the DMA byte count did not equal 0. When this occurs the transmitter stops without sending the CRC and the end
flag.
NOACK - The GSC sets this bit to indicate that an acknowledge was not received for the previous frame. This bit
will be set only if HABEN is set and no acknowledge is received before the end of the IFS. NOACK will not be set
following a broadcast or a multi-cast packet.
LNI - The GSC sets this bit to indicate that the receive line is idle. In CSMA/CD mode LNI is set if GRXD remains
high for ~ 1.6 bit times. LNI is cleared after a transition on GRXD. In SDLC node LNI is set if 15 consecutive ones
are received.
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