NEC UPD789026 Series, User Manual

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CHAPTER 2 PIN FUNCTIONS
User's Manual U11919EJ3V0UM00
36
2.2.4 P30 to P32 (Port 3)
These pins constitute a 3-bit I/O port. In addition, they also function as external interrupt input and capture edge
input.
This port can drive LEDs directly.
Port 3 can be specified in the following operation modes in bit-wise.
(1) Port mode
In this mode, port 3 functions as a 3-bit I/O port. Port 3 can be set in the input or output mode in 1-bit units
by using the port mode register 3 (PM3). When the port is used as an input port, an on-chip pull-up resistor
can be used in the pull-up resistor option register (PUO).
(2) Control mode
In this mode, port 3 functions as the external interrupt input.
(a) INTP0 to INTP2
These pins input external interrupt for which effective edges (rising edge, falling edge, and both the rising
and falling edges) can be specified.
(b) CPT2
This is a capture edge input pin.
2.2.5 P40 to P47 (Port 4)
These pins constitute an 8-bit I/O port. In addition, they also function as key return signal detection.
This port can drive LEDs directly.
Port 4 can be set in the following operation modes in bit-wise.
(1) Port mode
In this mode, port 4 functions as an 8-bit I/O port which can be set in the input or output mode in 1-bit units
by using the port mode register 4 (PM4). When used as an input port, an on-chip pull-up resistor can be
used in the pull-up resistor option register (PUO).
(2) Control mode
In this mode, the pins of port 4 can be used as key return signal detection pin (KR0 to KR7).
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