User:Myask/Universal Mapper Description Language

Details

Been thinking about making some better way to talk about mappers, as described in this post among several other places on our boards. Parts/functions

• Define state bits
  • include easy ROM/RAM chip(/internal) declaration; don't want to exclude MagicFloor nor MMC5/6 from "correct" description
• Logic
• Arbitrary address bus size for chips?

Convenience addtions

• Conditional operations (optional but helps user-side…but makes it harder program-side)
  • some header fields as parameters might be desirable (mirroring, chip sizes)
  • on the other hand, they are different boards in some manner. Perhaps only as solder-pad options?
• Cartridge connector pins as predefined signal names, or a module (to allow picking 60 or 72-pin)
• Option to autoconnect power, ground, address lines that are not in file
  • like connecting PPU_A[0:7] to CHR_ROM_A[0:7] if CHR_ROM_A[0:7] do not appear in the description)
  • Also autoconnect CIC

Extra function thoughts

• Outputs (e.g. LED)
• Inputs (e.g. DIPswitch, solder pads)
• Describing expansion port devices in similar manner
• Describing controller port devices in similar manner

Hard Part

• Expansion audio (analog, can involve extra oscillators as VRC7 audio does)

NROM-256 example

mapper NROM_256V begin
 //without autofills
//component section
 prgrom prg(32KiB); 
 //could also write 256Kib..but seems like a source of many typo problems
 //perhaps go by address line, data line counts?
 chrrom chr(8KiB);
 //only difference between PRG and CHR def'ns are its default connections
 //and outputs
 CIC cic(NES);//allow other chips I guess?

//dynamic components section
 solder h to connect CIRAM_A10 to PPU_A[10];
 solder v to connect CIRAM_A10 to PPU_A[11]; 
 init h iNES.6[0];
 init v ~iNES.6[0];
  //technically redundant per wiki as only V-using boards had solder pads?
  //make "to" as whitespace, allowing nice codelook but not requiring 
 connect CIRAM_CE_n to PPU_A13_n;

//connections: power
 connect VCC prg.vcc cic.vcc chr.vcc;
 connect GND prg.gnd cic.gnd chr.gnd;
  //allow multiple connections per statement
  //considering a shortform lke "=" for connect
//connections: CIC 
 //[omitted]
//connections: PRG
 connect prg.a[14:0] CPU_A[14:0];
 //NROM_128: connect prg.a[13:0] CPU_A[13:0];
 //and connect prg.a[14] VCC; //several ways to do it, really.
 connect prg.d[7:0] CPU_D[7:0];
 connect prg.oe_n prg.ce_n ROMSEL_n; //I suspect I've got these mildly wrong
//connections: CHR
 connect chr.a[12:0] PPU_A[12:0];
 connect chr.d[7:0] PPU_D[7:0];
 connect chr.oe_n chr.ce_n PPU_A[13];

end NROM_256V;