DM9008F datasheet(46/68 Pages) ETC

46 / 68 page

DM9008

ISA/Plug & Play Super Ethernet Contoller

Final

Version :DM9008-DS-F02

June 14, 2000

Remote Read Timing

1) The DMA reads a byte/word from local buffer memory

and writes the byte/word into the latch, increments the

DMA

address,

and

decrements

the

byte

count

(RBCR0, 1).

2) If the byte from local buffer memory is not available,

IOCHRDY will be pulled low to insert wait states to the

PC. The IOCHRDY is inactive when the byte is

available.

3) When the system reads the port, the read strobe

( IOR ) is used as an acknowledge by the remote

DMA.

Steps 1-3 are repeated until the remote DMA is finished.

Note that if a local DMA is in progress, the remote DMA is held

off until the local DMA is finished.

Remote Write Timing

A Remote Write operation transfers data from the I/O port to

the local buffer RAM. The system transfers a byte/word to the

latch via IOW , and this write strobe is detected by the ENC.

The remote DMA then holds off further transfers into the latch

until the current byte/word has been transferred from the latch,

after which the next transfer can begin.

1) The system

writes a byte/word into the latch.

DM9008

not

ready

the

byte/word,

IOCHRDY will be pulled low to insert wait states into

the PC. IOCHRDY is inactive when the byte/word is

accepted by DM9008.

2) The remote DMA reads the contents of the port and

writes

the

byte/word

local

buffer

memory,

increments the address,

and decrements the byte

count (RBCR0, 1).

Steps 1-2 are repeated until the remote DMA is finished.

Slave Mode Timing

When the PC reads or writes any internal registers of DM9008,

DM9008 becomes a bus slave. All register accesses are

byte-wide. The PC accesses internal registers with four

address lines, SA0-SA3, and IOR and IOW strobes. Since

DM9008 may be a local bus master when the PC attempts to

read or write to DM9008, or attempts to read Boot-ROM data,

IOCHRDY will be pulled low to hold off the PC until DM9008

leaves master mode.

Boot-ROM Data Read

The Boot-ROM data pins are connected to Memory Data pins

MD0-7. DM9008 transfers these data to SD0-7 if the PC

activates a memory read operation with the address in the

range of the Boot-ROM address space.

Hardware Reset

DM9008 will be reset if RST is high. The ENC module can also

be reset when the PC reads the RESET port, followed by an

IOW operation.

The following bits will be cleared or set when DM9008 is reset.

Reset Bits

Set Bits

TXP, STA

RD2, STP

ISR

RST

IMR

D0 - D6

DCR

LAS

TCR

LB1, LB0

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