DP83905AVQB datasheet(11/80 Pages) NSC

11 / 80 page

40 Functional Description (Continued)

16-BIT IO PORT COMPATIBLE MODE IO ADDRESS

MAPPING

This mode is compatible with Novell’s NE2000 The base

IO address of the ATLANTIC Controller is configured by

Configuration Register A (either upon power up or by soft-

ware writing to this register) At that address the following

structure appears

Base a 00H

DP8390

Core

Registers

Base a 0FH

Base a 10H

Data Transfer Port

Base a 17H

Base a 18H

Reset Port

Base a 1FH

FIGURE 5 IO Port Mode Register IO Map

The registers within this area are 8 bits wide but the data

transfer port is 16 bits wide The ATLANTIC Controller’s

registers can be programmed to control the passing of data

between its internal memory and the data transfer port By

accessing the data transfer port (using IO instructions) the

user can transfer data to or from the ATLANTIC Control-

ler’s internal memory The ATLANTIC Controller’s internal

memory map is as shown in

Figure 6

ATLANTIC Controller actually has a 64k address range but

only does partial decoding on these devices The PROM

data is mirrored at all decodes up to 4000H and the entire

map is repeated at 8000H To access either the PROM or

the RAM the user must initiate a Remote DMA transfer be-

tween the IO port and memory

On a remote read the ATLANTIC Controller moves data

from its internal memory map to the IO port and the host

system reads it by using an ‘‘INW’’ or ‘‘INSW’’ instruction

from the IO address of the data transfer port If the system

attempts to read the port before ATLANTIC Controller has

written the next word of data to it ATLANTIC Controller will

insert wait states into the system cycle using the CHRDY

0000H

D15

001FH

PROM

Aliased PROM

4000H

8kx16

Buffer RAM

7FFFH

8000H

Aliased PROM

C000H

Aliased

Buffer RAM

FFFFH

(a)

D15

1EH

57H

1CH

57H

RESERVED

0AH

E’net Address 5

08H

E’net Address 4

06H

E’net Address 3

04H

E’net Address 2

02H

E’net Address 1

00H

E’net Address 0

(b)

FIGURE 6 a) NIC Core’s Memory Map

b) 16-Bit Prom Map

DP83905AVQB Datasheet(PDF) 11 Page - National Semiconductor (TI)

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