PSD934210MIT datasheet(41/89 Pages) STMICROELECTRONICS

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PSD834F2V

The first configuration is 80C31 compatible, and

the bus interface to the PSD is identical to that

shown in Figure 19. The second and third configu-

rations have the same bus connection as shown in

Figure 17. There is only one Read Strobe (PSEN)

connected to CNTL1 on the PSD. The A16 con-

nection to PA0 allows for a larger address input to

the PSD. The fourth configuration is shown in Fig-

ure 20. Read Strobe (RD) is connected to CNTL1

and Program Select Enable (PSEN) is connected

to CNTL2.

The 80C251 has two major operating modes:

Page mode and Non-page mode. In Non-page

mode, the data is multiplexed with the lower ad-

dress byte, and Address Strobe (ALE/AS, PD0) is

active in every bus cycle. In Page mode, data (D7-

D0) is multiplexed with address (A15-A8). In a bus

cycle where there is a Page hit, Address Strobe

(ALE/AS, PD0) is not active and only addresses

(A7-A0) are changing. The PSD supports both

modes. In Page Mode, the PSD bus timing is iden-

tical to Non-Page Mode except the address hold

time and setup time with respect to Address

Strobe (ALE/AS, PD0) is not required. The PSD

access time is measured from address (A7-A0)

valid to data in valid.

Table 17. Interfacing the PSD with the 80C251, with One Read Input

Note: 1. The A16 and A17 connections are optional.

2. In non-Page-Mode, AD7-AD0 connects to ADIO7-ADIO0.

ADIO0

ADIO1

ADIO2

ADIO3

ADIO4

ADIO5

ADIO6

ADIO7

ADIO8

ADIO9

ADIO10

ADIO11

ADIO12

ADIO13

ADIO14

ADIO15

CNTL0 (WR)

CNTL1(RD)

CNTL 2(PSEN)

PD0- ALE

PD1

PD2

RESET

AD8

AD9

AD10

AD14

AD15

AD13

AD11

AD12

AD8

AD9

AD10

AD11

AD15

ALE

A16

AD14

AD12

AD13

P1.0

P1.1

P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

P3.0/RXD

P3.1/TXD

P3.2/INT0

P3.3/INT1

RST

A161

P0.1

P0.0

P0.2

P0.3

P0.4

P0.5

P0.6

P0.7

P2.0

P2.1

P2.2

P2.3

P2.4

P2.5

P2.6

P2.7

ALE

PSEN

RD/A16

PC0

PC1

PC3

PC4

PC5

PC6

PC7

PB0

PB1

PB2

PB3

PB4

PB5

PB6

PB7

PA0

PA1

PA2

PA3

PA4

PA5

PA6

PA7

80C251SB

PSD

RESET

P3.4/T0

P3.5/T1

RESET

PC2

AI02881C

A171

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