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Renesas RH850: FP5 Serial communication error


Progress window displays an error: Device FP5 query: FP5 Serial communication error! Please check External Oscillator and FP5 frequency (baudrate) settings. 

The error means that the device is not responding to FP5 commands.

Possible solution:

Incorrect oscillator frequency setting is the most common cause for the error.

1. Go to Hardware menu / CPU Options / Debugging.

2. Verify that the Ext. Oscillator clk setting matches the on-board quartz crystal connected to the RH850 device.

3. Power-cycle the RH850 target board and retry. Usually power-cycling is not needed, except for some rare persistent cases.

Other possible solutions:

For a problem analysis it is recommended to use winIDEA logging capability.

  • Hardware problem
  • Wrong device specified in winIDEA
  • If a debug connection works, but FP5 not, then the FLMD0 and FLMD1 pins should be checked.
  • If debug and FP5 connection are inoperational, then also RESET, TDI and TDO should be checked.


FP5 is short for the Renesas RH850 PG-FP5 serial protocol. It is intended for device flash factory programming. With winIDEA it is normally used when executing Python scripts to read and write device Option bytes or OPBTs, that define user configuration for the device.

Debug pins are used for the FP5 communication. To be able to communicate the device factory firmware needs to know the frequency of the external quartz oscillator, therefore, winIDEA communicates the value to the device firmware. This is the only way for the firmware to correctly configure a device PLL, and thus be able to communicate efficiently at high baudrates and program the device flash with correct timing parameters.

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