Do you need a quick and convenient way to test your most recent changes on Zeal 8-bit Computer using taking out the internal NOR flash? Then this programmable cartridge is for you! Thanks to its 512 NOR Flash, it is possible to extend the memory capability of your Zeal 8-bit Computer, it can either be mapped additionally to the motherboard's internal ROM, or, it can completely override it, very convenient to make it bootable!

This cartridge can, in theory, be used on any 8-bit computer or any hobby project thanks to its parallel interface. The connector follows the pinout of the Zeal 8-bit Computer's extension port, that you can find here https://zeal8bit.com/docs/ext_port/

Mapping the NOR Flash

The NOR flash on this cartridge needs to be mapped on the computer's memory in order to be visible by the CPU. Thanks to the 3 switches on the PCB, it is possible to configure this without soldering anything. Here is what each switch means:

• REP: When set to 0, the NOR Flash will override the motherboard's internal ROM. In other words, the cartridge replies to all the memory requests on the hardware address range 0x000000:0x7ffff. Please note that in this mode, the other two switches are ignored.
• A20 & A19: When REP is set to 1, both A19 and A20 let you choose the physical address where the cartridge should be mapped. Please note that in all cases, A21 must be 1, as such, the mapping will be as followed:

Note 1: The cartridge will only reply to memory requests, which is indicated by MEMREQ pin being low.

Note 2: WR pin of the flash is also connected, which means it is possible to flash it in-circuit!

How to read its data then?

This will depend on the 8-bit computer you are interfacing it with. If you are using Zeal 8-bit Computer with Zeal 8-bit OS running, you can use the following C snippet to map the cartridge to virtual address 0x8000 and start reading it:

/* Define this macro according to the switches and the table above */
#define CARTRIDGE_PHYS_ADDR 0x300000

uint8_t* virt_addr = (uint8_t*) 0x8000;
zos_err_t err = map(virt_addr, (uint32_t) CARTRIDGE_PHYS_ADDR);
if (err != ERR_SUCCESS) {
    printf("Could not map cartridge\n");
    exit(0);
}
/* Cartridge mapped in 0x8000, print its first 3 bytes */
printf("Bytes: %x %x %x\n", virt_addr[0], virt_addr[1], virt_addr[2]);

What is included?

This product includes:

• Zeal Cartridge PCB (assembled and tested)
• A logic chip (GAL16V8B)
• A 512KB NOR Flash (SST39SF040)

What is NOT included?

Zeal 8-bit Computer is not included in the package

Support, questions and community

Feel free to join the Zeal 8-bit community to get support, to propose some ideas, to help with the software or simply to discuss with people passionate about retro-computing and Zeal 8-bit Computer.

Join the community on: Youtube: https://www.youtube.com/@zeal8bit

Discord: https://discord.gg/CtyGsSkzDY

Github: https://github.com/Zeal8bit

Twitter: https://twitter.com/zeal8bit