DP8390D datasheet(19/56 Pages) NSC

19 / 56 page

100 Internal Registers (Continued)

103 Register Descriptions

COMMAND REGISTER (CR)

00H (READWRITE)

The Command Register is used to initiate transmissions enable or disable Remote DMA operations and to select register

pages To issue a command the microprocessor sets the corresponding bit(s) (RD2 RD1 RD0 TXP) Further commands may

be overlapped but with the following rules (1) If a transmit command overlaps with a remote DMA operation bits RD0 RD1

and RD2 must be maintained for the remote DMA command when setting the TXP bit Note if a remote DMA command is re-is-

sued when giving the transmit command the DMA will complete immediately if the remote byte count register have not been re-

initialized (2) If a remote DMA operation overlaps a transmission RD0 RD1 and RD2 may be written with the desired values

and a ‘‘0’’ written to the TXP bit Writing a ‘‘0’’ to this bit has no effect (3) A remote write DMA may not overlap remote read

operation or visa versa Either of these operations must either complete or be aborted before the other operation may start

Bits PS1 PS0 RD2 and STP may be set any time

76543210

PS1

PS0

RD2

RD1

RD0

TXP

STA

STP

Bit

Symbol

Description

STP

STOP

Software reset command takes the controller offline no packets will be received or

transmitted Any reception or transmission in progress will continue to completion before

entering the reset state To exit this state the STP bit must be reset and the STA bit must be

set high To perform a software reset this bit should be set high The software reset has

executed only when indicated by the RST bit in the ISR being set to a 1 STP powers up

high

Note

If the NIC has previously been in start mode and the STP is set both the STP and STA bits will remain set

STA

START

This bit is used to activate the NIC after either power up or when the NIC has been

placed in a reset mode by software command or error STA powers up low

TXP

TRANSMIT PACKET

This bit must be set to initiate transmission of a packet TXP is

internally reset either after the transmission is completed or aborted This bit should be set

only after the Transmit Byte Count and Transmit Page Start registers have been

programmed

Note

Before the transmit command is given the STA bit must be set and the STP bit reset

D3 D4 D5

RD0 RD1 RD2

REMOTE DMA COMMAND

These three encoded bits control operation of the Remote DMA

channel RD2 can be set to abort any Remote DMA command in progress The Remote Byte

Count Registers should be cleared when a Remote DMA has been aborted The Remote

Start Addresses are not restored to the starting address if the Remote DMA is aborted

RD2

RD1

RD0

Not Allowed

Remote Read

Remote Write (Note 2)

Send Packet

AbortComplete Remote DMA (Note 1)

Note 1

If a remote DMA operation is aborted and the remote byte count has not decremented to zero PRQ (pin 29

DIP) will remain high A read acknowledge (RACK) on a write acknowledge (WACK) will reset PRQ low

Note 2

For proper operation of the Remote Write DMA there are two steps which must be performed before using

the Remote Write DMA The steps are as follows

i) Write a non-zero value into RBCR0

ii) Set bits RD2 RD1 RD0 to 0 0 1

iii) Set RBCR0 1 and RSAR0 1

iv) Issue the Remote Write DMA Command (RD2 RD1 RD0 e 0 1 0)

D6 D7

PS0 PS1

PAGE SELECT

These two encoded bits select which register page is to be accessed with

addresses RA0 – 3

PS1

PS0

Reserved

DP8390D 数据表(PDF) 19 Page - National Semiconductor (TI)

DP8390D 数据表(HTML) 19 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

数据表下载