CHAPTER 2 PIN FUNCTIONS
User’s Manual U16898EJ3V0UD
25
2.2.7 X1 and X2
These pins connect an oscillator to oscillate the X1 input clock.
X1 and X2 also function as the P121 and P122, respectively. For the setting method for pin functions, see
CHAPTER 17 OPTION BYTE
.
Supply an external clock to X1.
Caution The P121/X1 and P122/X2 pins are pulled down during reset.
2.2.8 AV
REF
This pin inputs a reference voltage to the internal A/D converter. When the A/D converter is not used, connect this
pin to V
DD
.
2.2.9 V
DD
This is the positive power supply pin.
2.2.10 V
SS
This is the ground pin.
In the 78K0S/KA1+, V
SS
functions alternately as the ground potential of the A/D converter. Be sure to connect V
SS
to a stabilized GND (= 0 V).
2.3 Pin I/O Circuits and Connection of Unused Pins
Table 2-1 shows I/O circuit type of each pin and the connections of unused pins.
For the configuration of the I/O circuit of each type, refer to
Figure 2-1
.
Table 2-1. Types of Pin I/O Circuits and Connection of Unused Pins
Pin Name
I/O Circuit Type
I/O
Recommended Connection of Unused Pin
P20/ANI0 to P23/ANI3
11
Input: Independently connect to AV
REF
or V
SS
via a resistor.
Output: Leave open.
P30/TI000/INTP0
P31/TI010/TO00/INTP2
8-A
I/O
Input: Independently connect to V
DD
or V
SS
via a resistor.
Output: Leave open.
P34/RESET
2
Input
Connect to V
DD
via a resistor.
P40
P41/INTP3
P42/TOH1
P43/TxD6/INTP1
P44/RxD6
P45
8-A
Input: Independently connect to V
DD
or V
SS
via a resistor.
Output: Leave open.
P121/X1
P122/X2
16-B
Input:
Independently connect to V
SS
via a resistor.
Output: Leave open.
P123 8-A
I/O
Input: Independently connect to V
DD
or V
SS
via a resistor.
Output: Leave open.
P130 3-C
Output
Leave
open.
AV
REF
−
Input
Directly connect to V
DD
.