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Renesas RH850: FP5 errors


Possible solutions

Delayed power ON target

Because of the hardware limitation of the BlueBox, the application runs for a bit before starting FP5 access. During that time, an application could disable FP5 access to the target device, which is not restored even after reset (but only after the power cycle).

1. Turn OFF the device. 

2. Make sure that you have enabled Check Vref on startup in Hardware | CPU options | Hardware.

3. Open an OPBT plugin or run the script for disabling the ICUM.

4. When the progress bar shows the message Vref out of range. Waiting for 30s to turn ON the device, turn ON the device. FP5 access should now be OK.

Verify oscillator frequency

Progress window displays an error: Device FP5 query: FP5 Serial communication error! Please check External Oscillator and FP5 frequency (baudrate) settingsThe error means that the device is not responding to FP5 commands. Incorrect oscillator frequency setting is the most common cause of the error.

1. Go to Hardware | 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 the debug and FP5 connection are not operational, 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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