Chapter 1 Hardware Structure
Pad Name
I/O
Options
Description
OSC1 and OSC2 are connected to an external RC
network or external crystal (determined by configura-
tion option) for the internal system clock. For external
RC system clock operation, OSC2 is an output pin for
1/4 system clock. If an RTC oscillator on pins OSC3
and OSC4 is used as a system clock, then the OSC1
and OSC2 pins should be left floating.
OSC3 and OSC4 are connected to a 32768Hz crystal
to form a Real Time Clock for timing purposes or to
form a system clock.
Schmitt Trigger reset input, active low.
Positive power supply
Negative power supply, ground
OSC1
OSC2
I
O
Crystal or RC
OSC3
OSC4
RES
VDD
VSS
I
O
I
¾
¾
RTC or
System Clock
¾
¾
¾
Note
1. Each pin on PA can be programmed through a configuration option to have a wake-up function.
2. Only pins PA0~PA3, PC0~PC3 and PC4~PC7 have a pull-high resistor configuration option.
These pull-high options can only be selected if these four pins are configured as NMOS types.
If the pull-high option is selected then it will apply to all four pins, individual pins cannot be
selected to have pull-high resistors. If setup as CMOS outputs the pull-high configuration
option is disabled.
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