PSD813F1 datasheet(47/110 Pages) STMICROELECTRONICS

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PSD813F1

Data Byte Enable Reference

Microcontrollers have different data byte orienta-

tions. The following table shows how the PSD in-

terprets byte/word operations in different bus

WRITE configurations. Even-byte refers to loca-

tions with address A0 equal to zero and odd byte

as locations with A0 equal to one.

Table 16. Eight-Bit Data Bus

MCU Bus Interface Examples

Figure 23 to 26 show examples of the basic con-

nections between the PSD and some popular

MCUs. The PSD Control input pins are labeled as

to the MCU function for which they are configured.

The MCU bus interface is specified using the PS-

Dsoft Express Configuration.

The first configuration is 80C31-compatible, and

the bus interface to the PSD is identical to that

shown in Figure 23. The second and third configu-

rations have the same bus connection as shown in

Table 17., page 48. There is only one READ input

(PSEN) connected to the CNTL1 pin on the PSD.

The A16 connection to the PA0 pin allows for a

larger address input to the PSD. Configuration 4 is

shown in Figure 24., page 49. The RD signal is

connected to Cntl1 and the PSEN signal is con-

nected to the CNTL2.

80C31

Figure 23 shows the bus interface for the 80C31,

which has an 8-bit multiplexed address/data bus.

The lower address byte is multiplexed with the

data bus. The MCU control signals Program Se-

lect Enable (PSEN, CNTL2), Read Strobe (RD,

CNTL1), and Write Strobe (WR, CNTL0) may be

used for accessing the internal memory and I/O

Ports. The ALE input (pin PD0) latches the ad-

dress.

Figure 23. Interfacing the PSD with an 80C31

BHE

D7-D0

Even Byte

Odd Byte

EA/VP

RESET

INT0

INT1

P1.0

P1.1

P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

P0.0

P0.1

P0.2

P0.3

P0.4

P0.5

P0.6

P0.7

PA0

PA1

PA2

PA3

PA4

PA5

PA6

PA7

PB0

PB1

PB2

PB3

PB4

PB5

PB6

PB7

PC0

PC2

PC1

PC3

PC4

PC5

PC6

PC7

P2.0

P2.1

P2.2

P2.3

P2.4

P2.5

P2.6

P2.7

ADIO0

ADIO1

ADIO2

ADIO3

ADIO4

ADIO5

ADIO6

ADIO7

ADIO8

ADIO9

ADIO10

ADIO11

ADIO12

ADIO13

ADIO14

ADIO15

CNTL0 (WR)

CNTL1(RD)

CNTL2 (PSEN)

PD0-ALE

PD1

PD2

RESET

PSEN

ALE/P

TXD

RXD

RESET

AD0

AD1

AD2

AD3

AD4

AD5

AD6

AD7

AD0

AD1

AD2

AD3

AD4

AD5

AD6

AD7

PSD

80C31

AD7-AD0

AD[ 7:0]

A10

A11

A12

A13

A14

A15

PSEN

ALE

RESET

AI02880C

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