2-wire UART Serial Programming with RFP on RL78/G23

Hello,

RFP can support serial programming using 2-wire UART if the dedicated UART pins TOOLTxD and TOOLRxD are used:

But, isn't a specific sequence required on TOOL0 to enter programming mode before 2-wire communications can take place on Tx/Rx? RFP allows /RESET to be controlled but what physical pin would the TOOL0 signal come over from the PC?

TOOL0 should be handled accordingly so the device enters flash memory programming mode:

TOOL0 should be handled accordingly so the device enters flash memory programming mode:

But following the level on TOOL0 when /RESET goes low->high, (<1>, <2>) 1 byte of data is still required on TOOL0 to proceed to enter flash memory programming mode. How does that get from RFP to the target MCU?

As listed RFP supports 2-wire dedicated UART with TypeD connection settings:

For examples of recommended connections of type D, refer to the RL78 Debugging functions Using Serial port Application notes

However, I see no reason to prefer 2-wire UART over single wire UART for RFP connection. With a 2-wire connection you will just use 1 more pin for the same baud rate.

TOOL0 needs to be controlled by the programmer to set the mode.  Connect TOOL0 to the incoming TxD via a serial resistor.  The G23 Fast ProtoBoard is a suitable reference design (and is very low-cost).

There is sample code to use a Raspberry Pi to program RL78/G23:

• Sample Code

  Flash programmer with Raspberry Pi (RL78 Protocol C) - Sample Code

  ZIP1.29 MB Feb 28, 2024

  

Thanks AZ_Renesas & JimB. The tapping off of TOOL0 from Tx was the missing information I'd not appreciated.

FYI the reason for going for 2-wire is that it is a redesign of a legacy product which already has a 2-wire UART connection to a master MCU for comms/reprogramming.

Edit. I can now successfully connect to and blank check a RL78/G23 using the 2-wire UART and RFP without a debug probe.