HD404344R Datasheet, PDF (50/102 Pages) Renesas Technology Corp – 4-bit microcomputer has an A/D converter

HD404344R Series/HD404394 Series
Pull-Up MOS Transistor Control
Pull-up MOS, which can be controlled by software, is built into all input/output pins except R1₀–R2₃ of the
HD404394 series.
The on/off status of all pull-up MOS pins is controlled by bit 3 (MIS3) of the miscellaneous register (MIS:
$00C) and the port data registers (PDR) of each pin. Each pin can therefore independently switch between
with or without pull-up MOS (table 17 and figure 24).
The on/off status of each transistor and the peripheral function mode of each pin can be set independently.
Miscellaneous register (MIS: $00C)
Bit
3
2
1
Initial value
Read/Write
Bit name
0
W
MIS3
0
W
MIS2
0
W
MIS1
0
0
W
MIS0
MIS3
0
1
Pull-Up MOS
On/Off Selection
Pull-up MOS off
Pull-up MOS on
MIS2
0
1
PMOS On/Off
Selection for Pin R0₂/SO
On
Off
Programming MIS1 and MIS0 to 1 is prohibited.
Figure 24 Miscellaneous Register
How to Deal with Unused I/O Pins
When input/output pins are not being used and are left floating, it is necessary to set these pins to V_CC to
reduce the possibility of LSI malfunctions due to noise. This can be done by selecting pull-up MOS for the
pins or by connecting an external pull-up resistor of about 100 kΩ at each unused pin.
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