Datasheet

RL78/L12 CHAPTER 4 PORT FUNCTIONS

R01UH0330EJ0200 Rev.2.00 117

Dec 13, 2013

4.4.4 Connecting to external device with different potential (1.8 V, 2.5 V, 3 V)

It is possible to connect to an external device with a different potential (1.8 V, 2.5 V or 3 V) by changing EVDD to accord

with the power supply of the connected device. In products in which EV

DD cannot be specified independently, I/O

connection with an external device operating on 1.8 V, 2.5 V or 3 V is still possible via the serial interface and general-

purpose port by using port 1.

4.4.5 Handling different potential (1.8 V, 2.5 V, 3 V) by using I/O buffers

It is possible to connect an external device operating on a different potential (1.8 V, 2.5 V or 3 V) by switching I/O

buffers with the port input mode register (PIM1) and port output mode register (POM1).

When receiving input from an external device with a different potential (1.8 V, 2.5 V or 3 V), set the port input mode

When outputting data to an external device with a different potential (1.8 V, 2.5 V or 3 V), set the port output mode

DD tolerance

Note 1

/EVDD

tolerance

Note 2

) switching.

The connection of a serial interface is described in the following.

Notes 1. For 32-, 44-, 48-, and 52-pin products

2. For 64-pin products

(1) Setting procedure when using input pins of UART0, CSI00, and CSI01 functions for the TTL input buffer

In case of UART0: P11

In case of CSI00: P10, P11

In case of CSI01: P15, P16

<1> Using an external resistor, pull up externally the 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 PIM1 register to 1 to switch to the TTL input buffer. For V

IH and VIL, 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>