5.6 Port 5
Port 5 is a 3-bit input/output port that also provides input and output pins for the serial communi-
cation interface (SCI). The pin functions depend on control bits in the serial control register (SCR).
Pins not used for serial communication are available for general-purpose input/output. Table 5-13
lists the pin functions, which are the same in both the expanded and single-chip modes.
Table 5-13. Port 5 Pin Functions (Modes 1 to 3)
Usage
Pin functions
I/O port
P5
0
P5
1
P5
2
Serial communication interface
TxD
RxD
SCK
See section 8, “Serial Communication Interface” for details of the serial control bits. Pins used by
the serial communication interface are switched between input and output without regard to the
values in the data direction register.
Pins of port 5 can drive a single TTL load and a 30pF capacitive load when they are used as output
pins. They can also drive a Darlington pair.
Table 5-14 details the port 5 registers.
Table 5-14. Port 5 Registers
Name
Abbreviation
Read/Write
Initial value
Address
Port 5 data direction register
P5DDR
W
H'F8
H'FFB8
Port 5 data register
P5DR
R/W
H'F8
H'FFBA
Port 5 Data Direction Register (P5DDR)—H'FFB8
P5DDR is an 8-bit register that selects the direction of each pin in port 5. A pin functions as an
output pin if the corresponding bit in P5DDR is set to “1,” and as an input pin if the bit is cleared to
“0.”
Bit
7
6
5
4
3
2
1
0
—
—
—
—
—
P5
2
DDR P5
1
DDR P5
0
DDR
Initial value
1
1
1
1
1
0
0
0
Read/Write
—
—
—
—
—
W
W
W
96
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