The RC2014 Orton 3C ROM Module adds 16k ROM to the Orton 3C computer.
The 16k appears in low memory at 0x4000 – 0x7FFF, and is also duplicated in high memory from 0xC000 – 0xFFFF. A 128k 39SF010 flash ROM IC is used, and any of the 8 16k banks can be selected by jumpers on the PCB. A ZIF socket makes removing the chip for reprogramming very simple
Address lines A0 – A13 are used to address the ROM when A14 is high, thus putting it in to the 0x4000 – 0x7FFF or 0xC000 – 0xFFFF address space, depending on A15. This address space is covered by the RAM on the Orton 3 CPU /RAM Module, so the jumper to “Disable RAM 0x4000 – 0x7FFF” must be installed. Strictly speaking, this does not disable the RAM at this address, it just prevents it from being read from. If you write to that address space, it will still be written to RAM, however, all reads will come from ROM.
Software
The initial code for ROM can be found on Codeberg here https://codeberg.org/RC2014/RC2014_Orton_3C_Code/src/branch/main/16kROM
Please note that this is a very short basic list of simple routines. The software team at RC2014 Towers (Spencer) are not programmers. Therefor you are encouraged to write your own routines and update the ROM yourself. If you write anything that may be useful or of interest to others, please submit updates back to the Codeberg repo.
Bill Of Materials
1 Orton 3C ROM PCB
1 32 pin wide ZIF socket
1 14 pin narrow DIL socket
1 40 pin RA header
2 1N4148
1 10k resistor
1 100nf
1 ST39SF010
1 74HCT02
