CHAPTER
ELEVEN
USING THE JTAG CONNECTOR
The MEGA65 main board has a 12-pin JTAG connector, a standard for connecting test equipment to devices. It is not
intended for regular users of a device—but we MEGA65 owners are not regular users, are we?
With a JTAG USB adapter and software available on Filehost, you can connect your PC directly to the main board to:
• Upload and execute programs being cross-developed on a PC
• Transfer files between your PC and MEGA65 without removing the SD card
• Perform remote debugging on programs and the built-in MEGA65 utilities
• Upload ROMs and cores for testing
• Use your MEGA65 as a SID music player (!)
The MEGA65 does not have a user-accessible port for the JTAG connection. You will have to acquire a JTAG USB
adapter and a mini-USB cable, install it, and run the cable out the back of the MEGA65 case.
Tip: You can also use a more common USB UART adapter for most of the purposes described below (sending files
and commands). The adapter must output 3.3 volts, not 5 volts. Test your adapter with a volt meter before using. See
Use of an USB UART adapter as alternative to a JTAG adapter for instructions on how to wire a UART to the JTAG
connector pins. See also this article by RetroCombs.
Photos below show how to connect the TE0790-03 JTAG adapter.
Tip: For another version of these instructions with more photos, see JTAG adapter, how to plug and DIP switch
settings.
11.1 Acquiring a JTAG adapter
The XMOD FTDI JTAG Adapter TE0790-03 (Trenz Electronic) is compatible with the MEGA65. You might also be
able to order the TE0790-03 from DigiKey. As of this writing, this item is difficult to get due to supply chain issues.
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