HD64F3437TF16 Datasheet, PDF (138/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

7.2.4 Input Pull-Up Transistors
Port 1 has built-in programmable input pull-up transistors that are available in modes 2 and 3. The
pull-up for each bit can be turned on and off individually. To turn on an input pull-up in mode 2 or
3, set the corresponding P1PCR bit to 1 and clear the corresponding P1DDR bit to 0. P1PCR is
cleared to H'00 by a reset and in hardware standby mode, turning all input pull-ups off. In software
standby mode, the previous state is maintained.
Table 7.3 indicates the states of the input pull-up transistors in each operating mode.
Table 7.3 States of Input Pull-Up Transistors (Port 1)
Mode Reset Hardware Standby Software Standby Other Operating Modes
1
Off
Off
Off
Off
2
Off
Off
On/off
On/off
3
Off
Off
On/off
On/off
Notes: Off: The input pull-up transistor is always off.
On/off: The input pull-up transistor is on if P1PCR = 1 and P1DDR = 0, but off otherwise.
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