Peccost wrote:
nintendo2600 wrote:
Hey All,
A friend and I got these boards made up to make 2MB games alot
easier to build so you don't have to have a zillion wires all over
the place. Just burn your your 27c160 drop it in this bad boy
and solider it onto your choice snes pcb. Saves alot of time
and hassle and makes a much cleaner final project.
Hi, I read the specs sheet twice about the 27C160 and still can't understand your adapter wiring.
ByteVPP (pin32) is set to GND so Q15A-1 (pin 30) is used for adress Input A-1.
And why do you start your adress linking with Q15(A-1) to maskrom A0?
A negative 1?
Thanks for help
Think of it this way.....
In a 16 bit rom, you have addresses A0-A20. A20 being the highest address = 32mbit.
In an 8 bit rom, you have addresses A0-A21. A21 being the highest address = 32mbit.
When you use the Byte pin on a 16 bit rom to configure it to run in 8 bit mode..... You need an additional address line. So the A-1 is better described as "A before zero". So when he made his 27c160 adapter, he had to address shift the roms addresses to match the Snes buss addresses.
So Rom A-1 = Snes A0
Rom A0 = Snes A1
Rom A1 = snes A2
....
....
...
Rom A19 = snes A20. (16mbit/2mByte)
Rom A20 = snes A21. (32mbit/4mByte). This is if a 32mbit chip HAD a "Byte" pin which it doesn't -- at least not in a DIP package.
Edit: since 16mbit rom is max size in dip package that can utilize the "Byte" function, the highest address for the 27c160 would be A19