
CHAPTER 14 PORT FUNCTION
User’s Manual U12768EJ4V1UD
349
Port 0 includes the following alternate functions.
Table 14-2. Alternate Functions of Port 0
Pin Name
Alternate Function
I/O
PULL
Note
Remark
P00
NMI
P01
INTP0
P02
INTP1
P03
INTP2
P04
INTP3
Analog noise elimination
P05
INTP4/ADTRG
P06
INTP5/RTPTRG
Port 0
P07
INTP6
I/O
Yes
Digital noise elimination
Note
Software pull-up function
(1) Function of P0 pins
Port 0 is an 8-bit I/O port for which I/O settings can be controlled in 1-bit units. I/O settings are controlled via the
port 0 mode register (PM0).
In output mode, the values set to each bit are output to port 0 (P0). When using this port in output mode, either
the valid edge of each interrupt request should be made invalid or each interrupt request should be masked
(except for NMI requests).
When using this port in input mode, the pin statuses can be read by reading P0. Also, the P0 register (output
latch) values can be read by reading P0 while in output mode.
The valid edge of NMI and INTP0 to INTP6 are specified via rising edge specification register 0 (EGP0) and falling
edge specification register 0 (EGN0).
A pull-up resistor can be connected in 1-bit units when specified via pull-up resistor option register 0 (PU0).
When a reset is input, the settings are initialized to input mode. Also, the valid edge of each interrupt request
becomes invalid (NMI and INTP0 to INTP6 do not function immediately after reset).
(2) Noise elimination
(a) Elimination of noise from NMI and INTP0 to INTP3 pins
An on-chip noise eliminator uses analog delay to eliminate noise. Consequently, if a signal having a constant
level is input for longer than a specified time to these pins, it is detected as a valid edge. Such edge detection
occurs after the specified amount of time.
(b) Elimination of noise from INTP4 to INTP6, ADTRG, and RTPTRG pins
A digital noise eliminator is provided on chip.
This circuit uses digital sampling.
A pin’s input level is detected using a sampling clock (fxx), and noise
elimination is performed if the same level is not detected three times consecutively.