This cartridge supports 512kB of system programmable FLASH ROM utilizing the RoboCop (Zumwalt) banking system.
Banks are 16kB in size (technically, 16KiB - 256 bytes, since $ff00-$ffff is reserved for IO and vectors), which allows operation on all TANDY Color Computer models and the Dragon Data Dragon machines. FLASH ROM appears at location $c000 in the memory map, while the banking register appears at $ff40. The bits in the banking register are as follows:
| IO Location | Bit Location | Description |
|---|---|---|
| $ff40 | 4:0 | FLASH address lines A18-A14 |
| 7 | 1 = Programming Enabled |
The system is designed to utilize AM29F040B FLASH ROMs, but can also accommodate 16kB-512kB FLASH ROMs or EPROMs via J1-J5. Please see schematic for more details. If EPROMs are utilized, IC3 is not required (EPROMs cannot be system programmable)
To program please consult the AM29F040B datasheet for details, but essentially:
- set bit 7 to 1 and select bank in bank register
- via machine language, store the following values:
- store $aa in $c555
- store $55 in $c2aa
- store $a0 in $c555
- store desired value in $c000-$feff address ($fdff on Color Computer 3, I believe)
Sample stub code is available in the src/ directory. The programming must be precise and cannot easily be performed from BASIC[1].
[1]: To simplify construction and reduce cost, programming is enabled for all of $c000-$ffff. This includes the entire $ffxx IO region. Unless care is taken to disable BASIC or the IRQ handlers from accessing $ffxx regions while sending the special programming sequence, the sequence will be disrupted and programming will not occur.
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