Renesas rl78 User Manual

Page of 1004
 
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 EV
DD
 
 V
DD 
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
/EV
DD 
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>