Recommendation for Hardware Setup 32-Bit FR81S Family
Document No. 002-09375 Rev. *B
6
2.10
Mode Pins
The mode pins set the current operation mode for the MCU. For a minimal system, only two modes are necessary:
Flash-Asynchronous-Serial-Programming-Mode and Run Mode.
In the case, you use the Serial Programming Mode the MD-pins need pull-up/pull-down resistors (typically 2k7
resistors). In order to increase the protection against ESD and EMI effects the PCB tracks should be as short as
possible.
If the Serial Programming Mode is not used the MD-pins can be connected directly to Vcc or GND. Please refer to
Datasheet chapter “Handling devices” for further information.
The following settings are used for the both modes mentioned above:
Table 3. Mode Pin Settings (x: does not care)
Mode
P006
MD0
MD1
Serial Programming Mode
1
0
1
Run (Internal Vector Mode)
x
1
0
2.11
Not Connected Pins
In default state after power-on reset usually the GPIO pins are in high-z state.
If unused input pins are left open, they may cause a permanent damage to the device due to malfunction or latch-up.
Connect at least a 2k resistor to each unused pin in pull-up or pull-down configuration. Also, if I/O pins are not used,
they must be set to the output state for releasing or they must be set to the input state and treated in the same way as
for the input pins.
Concerning special use cases, it is referred to Port Input / Unused Pins / Latch-up for how to proceed with unused (not
connected) pins.
