User:Myask/Universal Mapper Description Language
Needed features
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)
Specification
Comments
//c-style /*and c-style*/ //Let's also treat all whitespace the same (except newlines terminating //, blocks) //and "to" should be ignored in whitespace
Declarations:
mapper name begin //contents end name;
The outer part. Technically a block started with begin/end. Name optional.
mem name (address lines, data lines, writable, class);
- writable can be RAM or ROM.
- Class can be PRG, CHR, VRAM, [audio?] and MISC. Class controls default connections, and helps make obvious to readers what a thing is.
(see NROM example for default connections. Any prg gets CPU_A, CPU_D, /ROMSEL ("ROMSEL_n"), and optionally the R/W signal if it's a RAM. chr/vram gets PPU_A, PPU_D, read/writes, and enable depending on PPU_A[13] (or /A13 if VRAM)
solder name to /*contents*/; //can block if desired dip name to /*contents*/; //can block if desired: same as solder for emulator
- dipswitch
Just different name, really both just a state-based if statement, and these state bits are not settable except hardware(emulator)-side, unlike…
register name; reg name;//short form
init name to value; //can refer to iNES header fields like mirroring
Not that iNES is something we want much of, but it'll cut down on file redundancy.
Statements:
connect x to y to z; //any size netlist, whitespace-separated = x y z; //shortform set name to value; //set a state bit <= x y; //shortform
Operators
bitwise & AND | OR ^ XOR ~ invert logical &&AND ||OR ^^XOR !not mathematical + - * binary operations, -negation {concatenate, concatenatee} [bus-index:range] {3 duplicate} //as in verilog
Execution blocks
on CPU_WRITE /*do stuff*/; on PPU_WRITE on CPU_READ on PPU_READ on CLOCK
Handy Shorthand Defines
bankreg name (which bus, width, address lines replaced, address mask selecting=equals what, which bus to write [inc A or D to write], mask to write=equals what,, written bits); fixedbank (which bus, width, address lines replaced=with what, address mask selecting=equals what);
e.g.
bankreg bnrom (CPU, 2, 16:15, 16'h8000=16'h8000, CPU_D, 16'h8000=16'h8000, CPU_D[1:0]);
bankreg bxrom (CPU, 8, 22:15, 16'h8000=16'h8000, CPU_D, 16'h8000=16'h8000, CPU_D[7:0]);
bankreg gnrom_cpu (CPU, 2, 16:15, 16'h8000=16'h8000, CPU_D, 16'h8000=16'h8000, CPU_D[5:4]); bankreg gnrom_ppu (PPU, 2, 14:13, 16'h2000=16'h0000, CPU_D, 16'h8000=16'h8000, CPU_D[1:0]);
bankreg magic_series_cpu (CPU, 7, 21:15, 16'h8000=16'h8000, CPU_D, 16'h8000=16'h8000, CPU_D[7:1]); bankreg magic_series_ppu (PPU, 8, 20:13, 16'h2000=16'h0000, CPU_D, 16'h8000=16'h8000, CPU_D[7:0]); bankreg unrom (CPU, 3, 16:14, 16'hC000=16'h8000, CPU_D, 16'h8000=16'h8000, CPU_D[2:0]); fixedbank unrom_hi (CPU, 3, 16:14=3'b111, 16hC000=16'hC000);
The idea here is that it autogenerates a register of appropriate width, and statements in ON_x_WRITE to write that register when its write mask equality is met, and sets the appropriate address lines when its select mask is met. fixedbank does not need a register, obviously.
NROM-256 example
mapper NROM_256V begin //without autofills //aside from the mirroring, strikes me as the same as "default connections"? //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;