DP83907 datasheet(33/70 Pages) NSC

33 / 70 page

50 Register Descriptions (Continued)

DATA CONFIGURATION REGISTER (DCR)

0EH (WRITE)

This Register is used to program the DP83907 for 8- or 16-bit memory interface select byte ordering in 16-bit applications and

establish FIFO thresholds The DCR must be initialized prior to loading the Remote Byte Count Registers LAS is set on

power up

FT1

FT0

ARM

LAS

BOS

WTS

Bit

Symbol

Description

WTS

WORD TRANSFER SELECT

0 Selects byte-wide DMA transfers

1 Selects word-wide DMA transfers

WTS establishes byte or word transfers for both Remote and Local DMA transfers

Note

When word-wide mode is selected up to 32k words are addressable A0 remains low

BOS

BYTE ORDER SELECT

0 MS byte placed on AD15–AD8 and LS byte on AD7–AD0 (32xxx 80x86)

1 MS byte placed on AD7–AD0 and LS byte on AD15–AD8 (680x0)

Ignored when WTS is low

LAS

LONG ADDRESS SELECT

0 Dual 16-bit DMA mode

1 Single 32-bit DMA mode

When LAS is high the contents of the Remote DMA registers RSAR0 1 are issued as A16–

A31 Power up high

LOOPBACK SELECT

0 Loopback mode selected Bits D1 and D2 of the TCR must also be programmed for

Loopback operation

1 Normal Operation

ARM

AUTO-INITIALIZE REMOTE

0 Send Command not executed all packets removed from Buffer Ring under program

control

1 Send Command executed Remote DMA auto-initialized to remove packets from Buffer

Ring

Note

Send Command cannot be used with 680x0 byte processors

D5 and D6

FT0 and FT1

FlFO THRESHOLD SELECT

Encoded FIFO threshold Establishes point at which the

memory bus is requested when filling or emptying the FIFO During reception the FIFO

threshold indicates the number of bytes (or words) the FIFO has filled serially from the

network before the FIFO is emptied onto the memory bus

Note

FIFO threshold setting determines the DMA burst length

Receive Thresholds

FT1

FT0

Word Wide

Byte Wide

1 Word

2 Bytes

2 Words

4 Bytes

4 Words

8 Bytes

6 Words

12 Bytes

During transmission the FIFO threshold indicates the number of bytes (or words) the FIFO

has filled from the Local DMA before being transferred to the memory Thus the transmission

threshold is 16 bytes less the received threshold

DP83907 датащи(PDF) 33 Page - National Semiconductor (TI)

DP83907 датащи(HTML) 33 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 57 58 59 60 61 62 63 64 65 66 67 68 69 70

датащи скачать

ссылки URL