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4.4.4 Connecting to external device with different power potential (2.5 V, 3 V)
When parts of ports 0 operate with V
2.5 V or 3 V power supply voltage are possible.
Regarding inputs, CMOS/TTL switching is possible on a bit-by-bit basis by port input mode registers (PIM0).
Moreover, regarding outputs, different power potentials can be supported by switching the output buffer to the N-ch
open drain (V
withstand voltage) by the port output mode registers (POM0).
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(1) Setting procedure when using I/O pins of UART1 and CSI10 functions
(a) Use as 2.5 V or 3 V input port
<1> After reset release, the port mode is the input mode (Hi-Z).
<2> If pull-up is needed, externally pull up the pin to be used (on-chip pull-up resistor cannot be used).
In case of UART1:
In case of CSI10:
<3> Set the corresponding bit of the PIM0 register to 1 to switch to the TTL input buffer.
<4> V
/V
operates on 2.5 V or 3 V operating voltage.
IH
IL
(b) Use as 2.5 V or 3 V output port
<1> After reset release, the port mode changes to the input mode (Hi-Z).
<2> Pull up externally the pin to be used (on-chip pull-up resistor cannot be used).
In case of UART1:
In case of CSI10:
<3> Set the output latch of the corresponding port to 1.
<4> Set the corresponding bit of the POM0 register to 1 to set the N-ch open drain output (V
voltage) mode.
<5> Set the output mode by manipulating the PM0 register.
At this time, the output data is high level, so the pin is in the Hi-Z state.
<6> Operation is done only in the low level according to the operating status of the serial array unit.
134
CHAPTER 4 PORT FUNCTIONS
= 4.0 V to 5.5 V, I/O connections with an external device that operates on a
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P03
P03, P04
P02
P02, P04
User's Manual U17854EJ9V0UD
withstand
DD
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