RL78/G13 CHAPTER 4 PORT FUNCTIONS
R01UH0146EJ0100 Rev.1.00 271
Sep 22, 2011
4.4.4 Connecting to external device with different potential (1.8 V, 2.5 V, 3 V)
When parts of ports 0, 1, 4, 5, and 14 operate with VDD = 4.0 to 5.5 V, I/O connections with an external device that
operates on 1.8 V, 2.5 V, 3 V power supply voltage are possible.
Regarding inputs, CMOS/TTL switching is possible on a bit-by-bit basis by the port input mode registers (PIM0, PIM1,
PIM4, PIM5, PIM8, PIM14).
Moreover, regarding outputs, different potentials can be supported by switching the output buffer to the N-ch open drain
(V
DD withstand voltage) by the port output mode registers (POM0, POM1, POM4, POM5, POM8, POM14).
(1) Setting procedure when using I/O pins of UART0 to UART3, CSI00, CSI01, CSI10, CSI20, CSI30, and CSI31
functions
(a) Use as 1.8 V, 2.5 V, 3 V input port
<1> If pull-up is needed, externally pull up the pin to be used (on-chip pull-up resistor cannot be used).
In case of UART0: P11
In case of UART1: P03 (P81)
In case of UART2: P14
In case of UART3: P143
In case of CSI00: P10, P11
In case of CSI01: P43, P44
In case of CSI10: P03, P04 (P80, P81)
In case of CSI20: P14, P15
In case of CSI30: P142, P143
In case of CSI31: P53, P54
<2> After reset release, the port mode is the input mode (Hi-Z).
<3> Set the corresponding bit of the PIM0, PIM1, PIM4, PIM5, PIM8, and PIM14 registers to 1 to switch to the
TTL input buffer.
<4> V
IH/VIL operates on 1.8 V, 2.5 V, 3 V operating voltage.
<R>
<R>
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