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RL78/G1A CHAPTER 4 PORT FUNCTIONS
R01UH0305EJ0200 Rev.2.00 116
Jul 04, 2013
4.4.4 Handling different potential (1.8 V or 2.5 V) by using EVDD ≤ VDD
When connecting an external device operating on a different potential (1.8 V or 2.5 V), it is possible to connect the
I/O pins of general ports by changing EV
DD0 to accord with the power supply of the connected device.
4.4.5 Handling different potential (1.8 V or 2.5 V) by using I/O buffers
It is possible to connect an external device operating on a different potential (1.8 V or 2.5 V) by switching I/O buffers
with the port input mode register (PIMxx) and port output mode register (POMxx).
When receiving input from an external device with a different potential (1.8 V or 2.5 V), set the port input mode registers
0 and 1 (PIM0 and PIM1) on a bit-by-bit basis to enable normal input (CMOS)/TTL input buffer switching.
When outputting data to an external device with a different potential (1.8 V or 2.5 V), set the port output mode registers
0, 1, and 7 (POM0, POM1, and POM7) on a bit-by-bit basis to enable normal output (CMOS)/N-ch open drain (V
DD
tolerance
Note 1
/EVDD tolerance
Note 2
) switching.
Following, describes the connection of a serial interface.
Notes 1. For 25- to 48-pin products
2. For 64-pin products
(1) Setting procedure when using input ports of UART0 to UART2, CSI00, CSI10, and CSI20 functions for the TTL
input buffer
In case of UART0: P11
In case of UART1: P03
In case of UART2: P14
In case of CSI00: P10, P11
In case of CSI10: P03, P04
In case of CSI20: P14, P15
<1> Using an external resistor, pull up externally the input pin to be used to the power supply of the target
device (on-chip pull-up resistor cannot be used).
<2> Set the corresponding bit of the PIM0 and PIM1 registers to 1 to switch to the TTL input buffer. For V
IH
and V
IL, refer to the DC characteristics when the TTL input buffer is selected.
<3> Enable the operation of the serial array unit and set the mode to the UART/CSI mode.
<R>
<R>
<R>
<R>