UPD78F1502AGK-GAK-AX Datasheet, PDF (214/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 4 PORT FUNCTIONS
4.4.4 Connecting to external device with different power potential (2.5 V, 3 V)
When parts of ports 1, 7, and 8 operate with VDD = 4.0 V to 5.5 V, I/O connections with an external device that operates
on a 2.5V 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 (PIM1 and PIM7).
Moreover, regarding outputs, different power potentials can be supported by switching the output buffer to the N-ch
open drain (VDD withstand voltage) by the port output mode registers (POM1, POM7 and POM8).
(1) Setting procedure when using I/O pins of UART1, UART2 CSI00, CSI01, CSI10, and CSI20 functions
(a) Use as 2.5V 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 UART2:
In case of CSI01:
In case of CSI10:
In case of CSI20:
P14
P11
P75, P76
P15, P14
P10, P11
<3> Set the corresponding bit of the PIMn register to 1 to switch to the TTL input buffer.
<4> VIH/VIL operates on a 2.5V or 3 V operating voltage.
Remark n = 1, 7
(b) Use as 2.5V 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 UART2:
In case of CSI00:
In case of CSI01:
In case of CSI10:
In case of CSI20:
P13
P12
P80, P82
P75, P77
P15, P13
P10, P12
<3> Set the output latch of the corresponding port to 1.
<4> Set the corresponding bit of the POMn register to 1 to set the N-ch open drain output (VDD withstand
voltage) mode.
<5> Set the output mode by manipulating the PMn 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.
Remark n = 1, 7, 8
R01UH0004EJ0501 Rev.5.01
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Jun 20, 2011