CHAPTER 14 PORT FUNCTION
User’s Manual U13850EJ4V0UM
376
Port 0 includes the following alternate functions.
Table 14-2. Port 0 Alternate Function Pins
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 the port 0 register (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 the P0 register. Also, the P0
register (output latch) values can be read by reading the P0 register 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 (f
XX
), and noise
elimination is performed for the INTP4, INTP5, ADTRG, and RTPTRG pins if the same level is not detected
three times consecutively. The noise-elimination width can be changed for the INTP6 pin (see
5.3.8 (3)
Noise elimination of INTP6 pin
).
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