CHAPTER 12: I/O Port
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 739
5. Usage Precautions
This section describes precautions for using the I/O port.
ON/OFF of the Pull-up Resistance When SPL=1
SPL is a signal for turning a pin into Hi-Z state during standby mode.
− When SPL=0 Normal operations
− When SPL=1 Pin Hi-Z, input cut-off, pull-up disconnection
However, the SPL bit cannot be used for setting external interrupts, NMIX, JTAG, or TRACE pins.
For details of the SPL bit, see Chapter "Low Power Consumption Mode".
DTTIX Input
DTTI input is an input signal for switching the dual-purpose motor control PWM output (RTO) setting
output pin to its other GPIO pin setting to address a motor stop demand in an emergency.
To use this function, enable switching by EPFR.
Procedures for Switching Pin Functions
When switching the outputs for peripheral functions using the EPFR register, to prevent pin uncertain
output (Hi-Z), switch settings according to the procedures similar to the switching example shown in the
following Figure 5-1.
Figure 5-1 Procedures for Switching Pin Functions
Reserved bit
This bit is read out as 0 except for that of ADE register. When writing, always write 0. The ADE reserved
bit is read out as 1. When writing, always write 1.
Connecting External Bus Pin and SRAM
When accessing SRAM via external bus, either perform pull-up setting for the pin or connect it to external
pull-up pin.
Multi-function Serial Pin Group
DDR Register Value
PDOR Register Value
EPFR Register Value
PFR Register Value
Pin Output Level
Pin Output Contents
Dontcare
Dontcare
Select Peripheral Macro A
1. Set to GPIO output direction (DDR=1)
2. Set GPIO output value using PDOR (inactive output value for peripheral function A)
4. Switch pin functions to GPIO (PFR=0)
Select Peripheral Macro B
5. Change pin function selection from A to B3.
3. Stop the output of peripheral function A
6. Set GPIO output value using PDOR
(Inactive output value of peripheral function B)
7. Switch pin functions to peripheral (PFR=1)
8. Start the output of peripheral function B
Peripheral Function A Output Peripheral Function B OutputGPIO Output
In order to avoid pin output uncertainty (Hiz) while switching EPFR settings,
switch EPFR pin settings after changing to GPIO setting (PFR=0).
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