Purpose

This is my interpretation of a simple cartridge for the X16 architecture. It is intended as a simple cart meant to be programmed within the X16 environment and has minimal components to achieve this goal.

History

The OtterX is an Commander X-16 clone that is fully compatible with the X16 architecture; once I completed construction of the computer the open-source way, I came up with this cartridge design to go with it.

To achieve this goal, I found a great lot of information on the git of jkominek - he has a very useful X16 expansion port & cartridge component/footprint library for KiCad 8 that I imported in kicad 10; he also has the basic design for a simple cartridge in PDF format, a great head start to design my X16 cartridge.

I started from that and designed the PCB in surface mount with the idea of being able to purchase a lot of PCBs pre-assembled using PCBA services.

I altered the footprint and routed the board by hand, keeping it 2-layer. I think I like the end result.

This PCB layout should fit a Muramasa Entertainment famicom cartridge shell, but this hasn't been tested yet.

The components goes face down to the rear of the cart, with the silkscreen label facing upward towards the label.

Bill of Material

The hardware included on the PCB is as follow

-SST39SF040-70-4C-NHE

--The FLASH memory, same type as on the CX16 or OtterX but in PLCC form

-24LC128-I/P

--I2C EEPROM to save on cart

-SN74ACT00D

--NAND gates (SOIC14) to assist with logic

-CD74ACT138M96

--Address decoder (SOIC16)

-CL21B105KBFNNNE (x2)

--1uF Decoupling capacitors

-CL21B104KBCNNNC (x4)

--100nF Decoupling capacitors

-RC0805FR-0710KL

--10k ohm pull-up resistor to put ROM read-only when JP1 is cut open

How to burn ROM cart

X16 onboard cards or carts can be written with the same X16 update utility used to update the VERA board or firmware ROM, the X16-FLASH utility

The software is intended to be part of the essential SD card software, but can also be found on git - here

Cartridge binaries would be saved alongside the software and written directly using the X16 hardware.

How to insert the cart

The SMD components are on what goes on the rear of the cart, with the full-cart silkscreen label being the front.

There is an indication for where the cart should point towards the rear of the computer. Depending on the cartridge slot utilized, this may mean the label pointing upwards or rightwards.