PSD412A2-C-90UI View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

PSD412A2-C-90UI

Low Cost Field Programmable Microcontroller Peripherals

STMicroelectronics 

PSD4XX Family

The PSD4XX

Architecture

(cont.)

9.2.4 Data Byte Enable

Microcontrollers have different data byte orientations with regard to the data bus. The

following tables show how the PSD4XX handles the byte enable under different bus

configurations. Even byte refers to locations with address A0 equal to “0”, and odd byte as

locations with A0 equal to “1”.

Table 7. 8-Bit Data Bus

BHE

A0

X

0

X

1

D7 – D0

Even Byte

Odd Byte

Table 8. 16-Bit Data Bus With BHE

BHE

A0

D15 – D8

0

0

Odd byte

0

1

Odd byte

1

0

–

D7 – D0

Even byte

–

Even byte

Table 9. 16-Bit Data Bus With WRH and WRL

WRH

WRL

0

0

0

1

1

0

D15 – D8

Odd byte

Odd byte

–

Table 10. 16-Bit Data Bus With SIZ0, A0

SIZ0

A0

0

0

1

0

1

1

D15 – D8

Even byte

Even byte

–

D7 – D0

Even byte

–

Even byte

D7 – D0

Odd byte

–

Odd byte

Table 11. 16-Bit Data Bus With UDS, LDS

LDS

UDS

D15 – D8

0

0

Even byte

1

0

Even byte

0

1

–

D7 – D0

Odd byte

–

Odd byte

42

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