• Firmware examination

    Keith03/10/2021 at 17:14 0 comments


    Read the development board firmware ROM and had a go at disassembly to get an idea of how it works. I used da65 from the cc65 suite, but this can only disassemble 65C02 code. The firmware is part 65C816 code, so that code disassembles incorrectly. 

    Although the firmware reserves 32K of the ROM, much of it is blank (0xFF) so the actual code is only about 1.6 K.

    It looks like the USB-interfacing VIA does not use the timers or interrupts, just polled. I need to check the VIA PCR register initialisation code to ascertain this.


    Disassembled code did not reassemble using '816-capable assemblers. Gordon Henderson provided the answer. Disassembly to 65C02 code produces some instructions that are not 65C816 instructions. My assumption that the 65C816 instruction set was an inclusive superset of the 65C02 is false!

    All the BBSn and BBRn are 'C02 instructions that have been replaced with other codes on the C816.

    Some hand disassembly later, I have some 65C816 source code that assembles. I have uploaded it.

  • Installing software tools

    Keith02/26/2021 at 02:37 0 comments


    Following instructions from here: https://wdc65xx.com/gettingstarted/816-sxb-getting-started/

    1. Download WDCTools Install WDCTools and set update preferences with the installer

    2. Download D2XX FTDI Driver

    3. Download the WDC Programming Manual (not required, but helpful resource)

    4. Download XLEDFLASH project (unzip into C:/wdc/W65C816SXB

    Done. Alas it is Windows only, so I hade to install on a spare i3 laptop instead of my i7 desktop.

    Now Find WDCTools Support  videos on YouTube

  • Purchasing

    Keith02/19/2021 at 03:25 0 comments

    2021-02-17 10:54

    W65C816SXB ordered from Tindie, for $68.16 plus £15 postage US to UK. Much cheaper than Mouser who were charging £111.48 including postage. 

    2021-02-17 19:16 Item dispatched! 

    2021-02-19 11:15 Item leaves USA!

    2021-02-24 21:19 Item clears customs and enters Royal Mail network.

    2021-02-25 Item arrives. Yay!