Figure 17. An Example of a Typical 8-bit Non-Multiplexed Bus Interface
PSD834F2V
MCU
D[ 7:0]
A[ 15:0]
WR
RD
BHE
ALE
RESET
PSD
ADIO
PORT
WR (CNTRL0)
RD (CNTRL1)
BHE (CNTRL2)
RST
ALE (PD0)
PORT D
PORT
A
PORT
B
PORT
C
D [ 7:0]
A[ 23:16]
(OPTIONAL)
AI02879C
Data Byte Enable Reference. MCUs have differ-
ent data byte orientations. Table 15 shows how
the PSD interprets byte/word operations in differ-
ent bus write configurations. Even-byte refers to
locations with address A0 equal to 0 and odd byte
as locations with A0 equal to 1.
Table 15. Eight-Bit Data Bus
BHE
A0
X
0
X
1
D7-D0
Even Byte
Odd Byte
Figure 18. MCU Bus Interface Examples
Figure 19 to Figure 22 show examples of the basic
connections 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.
80C31. Figure 19 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 Pro-
gram Select Enable (PSEN, CNTL2), Read Strobe
(RD, CNTL1), and Write Strobe (WR, CNTL0) may
be used for accessing the internal memory and I/
O Ports blocks. Address Strobe (ALE/AS, PD0)
latches the address.
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