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Table 2.5.1 Functions of ports P0 to P4 in each processor mode
Processor
modes
Pins
P0
P1
P2
P3
P4
Notes 1: P4
also functions as the clock
2
2: P4
functions as a programmable I/O port in the memory expansion mode, and that functions as the clock
2
selection. (Refer to "Chapter 12. CONNECTION WITH EXTERNAL DEVICES.")
3: This table lists a switch of pins' functions by switching the processor mode. Refer to the following section about the input/output
timing of each signal:
•"Chapter 12. CONNECTION WITH EXTERNAL DEVICES."
•"Chapter 15. ELECTRICAL CHARACTERISTICS."
CENTRAL PROCESSING UNIT (CPU)
Single-chip mode
P
P: Functions as a programmable
I/O port.
P
P: Functions as a programmable
I/O port.
P
P: Functions as a programmable
I/O port.
P
P: Functions as a programmable
I/O port.
P
P: Functions as a programmable
I/O port.
(Note 1)
output pin. (Refer to "Chapter 12. CONNECTION WITH EXTERNAL DEVICES.")
1
7751 Group User's Manual
2.5 Processor modes
Memory expansion/Microprocessor mode
• When external data bus width is 16 bits (BYTE = "L")
A
– A
8
15
• When external data bus width is 8 bits (BYTE = "H")
• When external data bus width is 16 bits (BYTE = "L")
A
– A
16
• When external data bus width is 8 bits (BYTE = "H")
A
– A
16
P3
3
ALE
P3
2
P3
1
P3
0
P4
– P4
3
7
P: Functions as a programmable I/O port.
P4
1
2
P4
1
P4
0
A
– A
0
7
D(odd)
D (odd): Data at odd address
A
– A
8
15
D(even)
23
D (even): Data at even address
D
23
D : Data
HLDA
BHE
R/W
P
(Note 2)
RDY
HOLD
output pin by software
1
2–25
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