PSD5XX Family
Bus
Interface
(Cont.)
30
9.2.3 PSD5XX Interface To Non-Multiplexed Bus
Figure 16 shows a PSD5XX interfacing to a microcontroller with a non-multiplexed
address/data bus. The address bus is connected to the ADIO Port, and the data bus is
connected to Port C and/or Port D, depending on the bus width. There is no need for the
ADIO Port to latch the address internally, but the user is offered the option to do so in the
PSD5XX PSDsoft Software. The data ports are in tri-state mode when the PSD5XX is not
accessed by the microcontroller.
9.2.4 Data Byte Enable
Microcontrollers have different data byte orientations with regard to the data bus. The
following tables show how the PSD5XX 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 6. 8-Bit Data Bus
BHE
A0
X
0
X
1
D7 – D0
Even Byte
Odd Byte
Table 7. 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 8. 16-Bit Data Bus With WRH and WRL
WRH
WRL
D15 – D8
0
0
0
1
1
0
Odd byte
Odd byte
–
D7 – D0
Even byte
–
Even byte
Table 9. 16-Bit Data Bus With SIZ0, A0
SIZ0
A0
D15 – D8
0
0
1
0
1
1
Even byte
Even byte
–
D7 – D0
Odd byte
–
Odd byte
Table 10. 16-Bit Data Bus With UDS, LDS
LDS UDS (A0)
D15 – D8
0
0
1
0
0
1
Even byte
Even byte
–
D7 – D0
Odd byte
–
Odd byte