
PSD4XX Famly
42
Table 7. 8-Bit Data Bus
Table 8. 16-Bit Data Bus With BHE
WRH
0
WRL
0
D15 – D8
Odd byte
D7 – D0
Even byte
0
1
Odd byte
–
1
0
–
Even byte
Table 9. 16-Bit Data Bus With WRHand WRL
SIZ0
A0
D15 – D8
D7 – D0
0
0
Even byte
Odd byte
1
0
Even byte
–
1
1
–
Odd byte
Table 10. 16-Bit Data Bus With SIZ0, A0
LDS
UDS
D15 – D8
D7 – D0
0
0
Even byte
Odd byte
1
0
Even byte
–
0
1
–
Odd byte
Table 11. 16-Bit Data Bus With UDS, LDS
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”.
BHE
A0
D15 – D8
D7 – D0
0
0
Odd byte
Even byte
0
1
Odd byte
–
1
0
–
Even byte
BHE
A0
D7 – D0
X
0
Even Byte
X
1
Odd Byte
The PSD4XX
Architecture
(cont.)