NEC UPD789026 Series, User Manual

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CHAPTER 2 PIN FUNCTIONS
User's Manual U11919EJ3V0UM00
37
2.2.6 P50 to P53 (Port 5)
These pins constitute a 4-bit I/O port. In addition, these pins provide the function for performing input/output
to/from the timer.
This port can drive LEDs directly.
Port 5 can be specified in the following operation modes in bit-wise.
(1) Port mode
In this mode, port 5 functions as a 4-bit I/O port. Port 5 can be set in the input or output mode in 1-bit units
by using the port mode register 5 (PM5). 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 5 functions as the timer input/output.
(a) TI0
This is the external clock input pin for 8-bit timer/event counter.
(b) TO0
This is an 8-bit timer output pin.
(C) TO2
This is a 16-bit timer output pin.
2.2.7 RESET
This pin inputs an active-low system reset signal.
2.2.8 X1, X2
These pins are used to connect a crystal resonator for system clock oscillation.
To supply an external clock, input the clock to X1 and input the inverted signal to X2.
2.2.9 NC
The NC (Non-connection) pin is not connected internally. Connect this pin directly to the V
SS
pin (it can also be
left open).
2.2.10 V
DD
Positive power supply pins
2.2.11 V
SS
Ground potential pins
2.2.12 V
PP
(
µµµµ
PD78F9026A only)
A high voltage should be applied to this pin when the flash memory programming mode is set and when the
program is written or verified.
Directly connect this pin to the V
SS0
or V
SS1
pin in the normal operating mode.
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