The PG-FP4 (made by Renesas Electronics) and the FL-PR4 (made by Naito Densei Machida Mfg. Co., Ltd.) programmers can also be used for on-board programming.
Regarding specific connections to the programmer, the serial signal line and power supply (used to check if power is supplied to the device), as well as the ground, reset signal, and VPP are connected, as described in the device data sheets and other documents.
Regarding the CPU clock, the on-board clock can be used.
The reset signal and VPP signal connected to the programmer are signals that must be used in the normal operating status.
So, you must design so that reset can also be applied from the programmer in addition to regular reset.
However, since there are time restrictions regarding switching from reset release to the programming mode, design the system so that the time from when the programmer releases reset until device reset is released is not too long.
Also, since VPP is normally connected to VSS, implement a design with a switch that can be activated with a jumper so as to enable connection to the programmer during programming, and connection to VSS during normal operation.
Also, implement unused pin processing for the serial signal used during programming if it is not used, and make it possible to switch it during write if it is used for normal operation.