N S 7 5 2 0 D R A M a d d r e s s m u l t i p l e x i n g

 

NS7520 multiplexed address outputs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NS7520

A23

A22

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

pin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DRAM

 

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

 

pin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RAS

 

22

21

20

19

18

17

16

15

14

13

12

11

10

9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CAS

 

22

0

0

0

10

9

8

7

6

5

4

3

2

1

 

 

 

 

 

 

 

 

 

 

 

16-bit DRAM peripheral (22 address bits: 14 RAS and 8 CAS)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NS7520

A23

A22

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

pin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DRAM

A13

A12

A11

A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

 

 

pin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RAS

23

22

21

20

19

18

17

16

15

14

13

12

11

10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CAS

23

22

0

0

0

10

9

8

7

6

5

4

3

2

 

 

 

 

 

 

 

 

 

 

 

 

32-bit DRAM peripheral (22 address bits: 14 RAS and 8 CAS)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 41: Internal DRAM multiplexing — Mode 1

Using the external multiplexer

An external address multiplexer is required when the selected SDRAM component cannot interface with the NS7520 internal multiplexer. Although an external address multiplexer is used, the NS7520 memory controller can control the basic DRAM signal protocol. The NS7520 can be configured to output the DRAM address multiplexer signal out the PORTA2 pin, by setting the AMUX or AMUX2 bit in the MMCR or by setting the DMUXS bit in the Chip Select Base Address register.

Setting the AMUX bit indicates that the internal address multiplexer must be disabled. When AMUX is set, the NS7520 drives the address bus using standard addressing without any multiplexing, the internal multiplexer is disabled, and the multiplexer indicator is driven out the PORTA2 pin.

The AMUX2 bit allows the internal bus masters to use the internal address multiplexer, and forces the PORTA2 signal to be driven.

1 0 8

N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v . D 0 3 / 2 0 0 6

Page 122
Image 122
Digi NS7520 manual Using the external multiplexer