91C94 datasheet(57/120 Pages) SMSC

57 / 120 page

I/O SPACE - BANK2

OFFSET

8 & A

NAME

DATA REGISTER

TYPE

READ/WRITE

SYMBOL

DATA

HIGH

BYTE

DATA HIGH

LOW

BYTE

DATA LOW

DATA REGISTER - Used to read or write the

data buffer byte/word presently addressed by

the pointer register.

This register is mapped into two uni-directional

FIFOs that allow moving words to and from the

LAN91C94 regardless of whether the pointer

address is even or odd. Data goes through the

write FIFO into memory, and is pre-fetched from

memory into the read FIFO.

If byte accesses

are used, the appropriate (next) byte can be

accessed

through

the

Data

Low or

Data High registers. The order to and from the

FIFO is preserved. Byte and word accesses can

be mixed on the fly in any order.

This register is mapped into two consecutive

word locations to facilitate the usage of double

word move instructions. The DATA register is

accessible at any address in the 8 through Ah

range,

while

the

number

bytes

being

transferred are determined by A0 and nSBHE in

ISA mode, and by A0, nCE1 and nCE2 in

PCMCIA mode.

91C94 Datasheet(PDF) 57 Page - SMSC Corporation

91C94 Datasheet(HTML) 57 Page - SMSC Corporation

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