
CHAPTER 5 PORT FUNCTIONS
111
5.4 PORT 2
Port 2 is an 8-bit input-only port. P22 to P27 incorporate a software programmable pull-up resistor. As well as operating as
input ports, port 2 pins also operate as control signal input pins, such as external interrupt signal pins (see Table 5-5). All 8 pins
are Schmitt-triggered inputs to prevent misoperation due to noise.
Table 5-5 Port 2 Operating Modes
Port Name
Function
P20
Input port/NMI input
Note
P21
Input port/INTP0 input/CR11 capture trigger input
Timer/counter 1 count clock/real-time output port trigger signal
P22
Input port/INTP1 input/CR22 capture trigger input
P23
Input port/INTP2 input/CI input
P24
Input port/INTP3 input/CR02 capture trigger input/
Timer/count 0 count clock
P25
Input port/INTP4 input/ASCK input/SCK1 input/output
P26
Input port/INTP5 input/A/D converter external trigger input
P27
Input port/SI0 input
Note
NMI input is acknowledged regardless of whether interrupts are enabled or disabled.
(a) Function as port pins
The pin level can always be read or tested regardless of the alternate-function pin operation.
(b) Functions as control signal input pins
(i)
NMI (Non-maskable Interrupt)
The external non-maskable interrupt request input pin. Rising edge detection or falling edge detection can be
specified by means of the external interrupt mode register 0 (INTM0).
(ii) INTP0 to INTP5 (Interrupt from Peripherals)
External interrupt request input pins. When the valid edge specified by the external interrupt mode registers 0,
1 (INTM0/INTM1) is detected an interrupt is generated (see
CHAPTER 21 EDGE DETECTION FUNCTION
).
In addition, pins INTP0 to INTP3 and INTP5 are also used as external trigger input pins with the various functions
shown below.
INTP0 ....... Timer/counter 1 capture trigger input pin
External count clock input pin
Real-time output port trigger input pin
INTP1 ....... Timer/counter 2 capture register (CR22) capture trigger input pin
INTP2 ....... Timer/counter 2 external count clock input pin
Capture/compare register (CR21) capture trigger input pin
INTP3 ....... Timer/counter 0 capture trigger input pin
Timer/counter 0 external count clock input pin
INTP5 ....... A/D converter external trigger input pin