LAN91C100FD datasheet(30/67 Pages) SMSC

30 / 67 page

SMSC DS – LAN91C100FD REV. B

Page 30

Rev. 01-20-06

BANK 2

OFFSET

NAME

TYPE

SYMBOL

FIFO PORTS REGISTER

READ ONLY

FIFO

This register provides access to the read ports of the Receive FIFO and the Transmit completion FIFO. The packet

numbers to be processed by the interrupt service routines are read from this register.

HIGH

BYTE

REMPTY

RX FIFO PACKET NUMBER

LOW

BYTE

TEMPTY

TX DONE PACKET NUMBER

REMPTY - No receive packets queued in the RX FIFO. For polling purposes, uses the RCV_INT bit in the Interrupt Status

TOP OF RX FIFO PACKET NUMBER - Packet number presently at the output of the RX FIFO. Only valid if REMPTY is

clear. The packet is removed from the RX FIFO using MMU Commands 3) or 4).

TEMPTY - No transmit packets in completion queue. For polling purposes, uses the TX_INT bit in the Interrupt Status

TX DONE PACKET NUMBER - Packet number presently at the output of the TX Completion FIFO. Only valid if TEMPTY

is clear. The packet is removed when a TX INT acknowledge is issued.

Note: For software compatibility with future versions, the value read from each FIFO register is intended to be written into

the PNR as is, without masking higher bits (provided TEMPTY and REMPTY = 0 respectively).

BANK 2

OFFSET

NAME

TYPE

SYMBOL

POINTER REGISTER

READ/WRITE

NOT EMPTY is a read

only bit

PTR

HIGH

BYTE

RCV

AUTO

INCR.

READ

ETEN

NOT

EMPTY

POINTER HIGH

LOW

BYTE

POINTER LOW

POINTER REGISTER - The value of this register determines the address to be accessed within the transmit or receive

areas. It will auto-increment on accesses to the data register when AUTO INCR. is set. The increment is by one for every

byte access, by two for every word access, and by four for every double word access. When RCV is set the address refers

to the receive area and uses the output of RX FIFO as the packet number, when RCV is clear the address refers to the

transmit area and uses the packet number at the Packet Number Register.

READ - Determines the type of access to follow. If the READ bit is high the operation intended is a read. If the READ bit is

low the operation is a write. Loading a new pointer value, with the READ bit high, generates a pre-fetch into the Data

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