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M16C/64A Group
Table 13.15
Unassigned Pin Handling in Memory Expansion Mode and Microprocessor Mode
Pin Name
Ports P0 to P5
Ports P6 to P10
BHE , ALE, HLDA , XOUT
HOLD , RDY
XIN
AVCC
AVSS, VREF
Notes:
1.
When setting a port to output mode and leaving it open, be aware that the port remains in input mode until it
is switched to output mode by a program after reset. For this reason, the voltage level on the pin becomes
undefined, causing the power supply current to increase while the port remains in input mode.
Furthermore, since the values of the direction registers can be changed by noise or noise-induced loss of
control, it is recommended that the values of the direction registers be regularly reset in software to improve
the reliability of the program.
2.
Connect unassigned pins with shortest possible wiring from the MCU pins (maximum 2 cm).
3.
When the CNVSS pin has the VSS level applied to it, these pins are set as input ports until the processor
mode is switched by a program after reset. For this reason, the voltage levels on these pins become
undefined, causing the power supply current to increase while they remain set as input ports.
4.
Ports P7_0, P7_1, and P8_5 are N-channel open drain outputs. When ports P7_0, P7_1, and P8_5 are set
to output mode, make sure a low is output from the pins.
5.
This applies when an external clock is input to the XIN pin or when VCC1 is connected via a resistor.
6.
When the PM07 bit in the PM0 register is 1 (BCLK not output), connect it to VCC2 via a resistor (pull-up).
Figure 13.16 Unassigned Pin Handling in Memory Expansion Mode and Microprocessor Mode
R01UH0136EJ0210 Rev.2.10
Jul 31, 2012
One of the following:
•
Set to input mode and connect a pin to VSS via a resistor (pull-down)
•
Set to input mode and connect a pin to VCC2 via a resistor (pull-up)
•
Set to output mode and leave the pins open
One of the following:
•
Set to input mode and connect a pin to VSS via a resistor (pull-down)
•
Set to input mode and connect a pin to VCC1 via a resistor (pull-up)
•
Set to output mode and leave the pins open
(5)
(6)
Open
, BCLK
Connect to VCC2 via a resistor (pull-up)
Connect to VCC1 via a resistor (pull-up)
Connect to VCC1
Connect to VSS
MCU
Ports P6 to P10
(Input mode)
(Input mode)
(Output mode)
Memory expansion mode or
microprocessor mode
Connection
.
.
.
.
.
.
VCC1
Open
XIN
BHE
HLDA
Open
ALE
XOUT
VCC2
BCLK
HOLD
VCC1
RDY
AVCC
AVSS
VREF
13. Programmable I/O Ports
(2)
(1, 3)
(1, 4)
VSS
Page 189 of 800
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