Hi guys. I have successifully completed 2 NROM devcarts so far, but that was easy because they didn't need any rewiring for use with the Flash ROMs I have.
Yesterday, I tried something more difficult, and removed the ROMs of a TLROM cart. The largest chips I have around are W27E512, wich are 64KBytes and can be erased with the EPROM programmer. I figured it'd be OK, I'd be using half the capacity of the board, but that's OK.
This chip's pinouts go like this:
I was happy, because it almost matches the NES ROM, except pin 22 is not A16, it's OE. Since I usually see OE beeing connected to GND, I did that, and left hole 22 empty.
As for the CHR part, It puzzles me why Nintendo used different chips if they are the same size. Does anyone know why? Anyway, if I placed my chip on the bottom 28 pins, CE and OE would be on the wrong place, and would have to be soldered to holes 31 and 02, respectivelly.
It all seemed fine to me, except it didn't work. All I got was a grey screen. I wasn't upset or anything, 'cause I kinda expected that to happen. Do you see anything wrong with what I did? In the PRG chip, is OE supposed to be connected to GND? Does anything else need to be done?
Thanks for the help again.
Oh, and what does an "/" mean on these pinouts? I don't understand why there is a pin (31) in the CHR ROM labeled "/A13".
Yesterday, I tried something more difficult, and removed the ROMs of a TLROM cart. The largest chips I have around are W27E512, wich are 64KBytes and can be erased with the EPROM programmer. I figured it'd be OK, I'd be using half the capacity of the board, but that's OK.
This chip's pinouts go like this:
Code:
---_---
A15 - |01 28| - Vcc
A12 - |02 27| - A14
A7 - |03 26| - A13
A6 - |04 25| - A8
A5 - |05 24| - A9
A4 - |06 23| - A11
A3 - |07 22| - OE/Vpp
A2 - |08 21| - A10
A1 - |09 20| - CE
A0 - |10 19| - Q7
Q0 - |11 18| - Q6
Q1 - |12 17| - Q5
Q2 - |13 16| - Q4
GND - |14 15| - Q3
-------
A15 - |01 28| - Vcc
A12 - |02 27| - A14
A7 - |03 26| - A13
A6 - |04 25| - A8
A5 - |05 24| - A9
A4 - |06 23| - A11
A3 - |07 22| - OE/Vpp
A2 - |08 21| - A10
A1 - |09 20| - CE
A0 - |10 19| - Q7
Q0 - |11 18| - Q6
Q1 - |12 17| - Q5
Q2 - |13 16| - Q4
GND - |14 15| - Q3
-------
I was happy, because it almost matches the NES ROM, except pin 22 is not A16, it's OE. Since I usually see OE beeing connected to GND, I did that, and left hole 22 empty.
As for the CHR part, It puzzles me why Nintendo used different chips if they are the same size. Does anyone know why? Anyway, if I placed my chip on the bottom 28 pins, CE and OE would be on the wrong place, and would have to be soldered to holes 31 and 02, respectivelly.
It all seemed fine to me, except it didn't work. All I got was a grey screen. I wasn't upset or anything, 'cause I kinda expected that to happen. Do you see anything wrong with what I did? In the PRG chip, is OE supposed to be connected to GND? Does anything else need to be done?
Thanks for the help again.
Oh, and what does an "/" mean on these pinouts? I don't understand why there is a pin (31) in the CHR ROM labeled "/A13".