FDT is the renesas tool that can talk to the processor in your target board and will read and write the flash memory on the chip. It can handle the full range of Renesas flah processors and is freely available for the renesas site although you will have to find your way round their site a bit. It is not possible to give a direct links as they require a registration form to be completed before you can download the file.
I downloaded FDT 3.05 and ran the installer. You can accept all the default settings for kernels and just allow the install to proceed although that means it will take quite a while as support for a very large number of processors is included. Not to worry - you may want them later.
Once FDT is installed, look in your start menu and you will see there are two ways to run it. We will select the Basic version. the first time it is run, a series of dialogs will allow you to configure the sogtware for your target board. We are going to be using a H8/3664F board for most projects so the dialogs will look like this:
All these settings can be changed later from the options menu.
The standard mode of FDT is more complicated than the Basic mode and is probably not necessary for any projects where the flash image is a single file.