LAN91C96I Datasheet, PDF (36/110 Pages) SMSC Corporation – NON-PCI SINGLE-CHIP FULL DUPLES ETHERNET CONTROLLER

Non-PCI Single-Chip Full Duplex Ethernet Controller
Note:
NOCRC - Does not append CRC to transmitted frames when set, allows software to insert the desired
CRC. Defaults to zero, namely CRC inserted.
FDSE - Full Duplex Switched Ethernet. When set, the LAN91C96I is configured for Full Duplex Switched
Ethernet, it defaults clear to normal CSMA/CD protocol. In FDSE mode the LAN91C96I transmit and
receive processes are fully independent, namely no deferral and no collision detection are implemented.
When FDSE is set, FDUPLX is internally assumed high and MON_CSN is assumed low regardless of their
actual values.
ETEN-TYPE - Early transmit underrun function type. When low, ETEN bit in the PTR register will enable
the Early transmit underrun function as it was implemented in the LAN91C94. I.e. “The Early Transmit
function allows the CPU to enqueue the first transmit packet before it is fully loaded in packet memory.
The loading operation proceeds in parallel with the transmission, and in the case that the transmitter gets
ahead of the CPU, the LAN91C96I will prevent the transmission of erroneous data by forcing an Underrun
condition. Underruns will be triggered by starving the transmit DMA if the LAN91C96I detects that the
DMA TX address exceeds the pointer address.”
With ETEN-TYPE set to one (1), ETEN bit set to one(1) in the pointer register will mean the following:
“For underrun detection purposes the RAM logical address and packet numbers of the packet being
loaded are compared against the logical address and packet numbers of the packet being transmitted. If
the packet numbers match and the logical address of the packet being transmitted exceeds the address
being loaded, the LAN91C96I will prevent the transmission of erroneous data by forcing an Underrun
condition. Underruns will be triggered by starving the transmit DMA if the LAN91C96I detects that the
DMA TX address exceeds the pointer address.”
The bit may be available for chips with Rev. ID 6 only and may be assigned to a different function in the
future.
EPH_LOOP - Internal loopback at the EPH block. Does not exercise the encoder decoder. Serial data is
looped back when set. Defaults low. Note: After exiting the loopback test, an SRESET in the ECOR or the
SOFT_RST in the RCR must be set before returning to normal operation.
STP_SQET - Stop transmission on SQET error. If set, stops and disables transmitter on SQE test error.
Does not stop on SQET error and transmits next frame if clear. Defaults low.
FDUPLX - When set it enables full duplex operation. This will cause frames to be received if they pass the
address filter regardless of the source for the frame. When clear the node will not receive a frame sourced
by itself. Clearing this bit (Normal Operation), allows in promiscuous mode, not to receive it’s own packet.
TXP_EN - This bit is reserved and should always be set to 0 on the LAN91C96I.
MON_CSN - When set the LAN91C96I monitors carrier while transmitting. It must see its own carrier by
the end of the preamble. If it is not seen, or if carrier is lost during transmission, the transmitter aborts the
frame without CRC and turns itself off.
When this bit is clear the transmitter ignores its own carrier. Defaults low.
PAD_EN - When set, the LAN91C96 will pad transmit frames shorter than 64 bytes with 00. For TX, CPU
should write the actual BYTE COUNT before padded by the LAN91C96 to the buffer RAM, excludes the
padded 00. When this bit is cleared, the LAN91C96 does not pad frames.
FORCOL - When set the transmitter will force a collision by not deferring deliberately. After the collision
this bit is reset automatically. This bit defaults low to normal operation.
LOOP - Local Loopback. When set, transmit frames are internally looped to the receiver after the
encoder/decoder. Collision and Carrier Sense are ignored. No data is sent out. Defaults low to normal
mode.
Rev. 11/18/2004
Page 36
DATASHEET
SMSC DS – LAN91C96I