> Thanks for all your help! Have you built this project? How well did it
work?
You are welcome. I didn't build this project, but I can tell you how it
works. When you place the SRAM Cart in the Base (BASE.PCX circuit), it's
powered by the +5V line. So you can transfer the data (.BIN ROM file) to the
SRAM Cart. When you remove the SRAM Cart from the Base, the SRAM still
retain the data because it will stay in stand-by mode, thanks to the Batt.
The Cart Connector Pin 12 is tied to ground in the VCS, but it's used to
write enable the SRAM in the Base.
> I took a Pac Man apart, and desoldered the ROM chip. I dug through my bin
of
> scavenged chips, and found some SRAM's They are UM61256AK-15's. I checked
on
> the 'net, and they are 32k*8 SRAM chips. Will the larger chips work as
8k*8
> chips?
Yes, but you'll have to make some modifications in the circuit. See the
following circuit:
Cart +---+--+---+
Con.----1A |1 +--+ 14| VCC
Pin 6 /1Y |2 13| 6A
(A12) 2A |3 12| /6Y
/2Y |4 7414 11| 5A
3A |5 10| /5Y
/3Y |6 9| 4A
GND |7 8| /4Y
+----------+
+-----+--+-----+
.----A14 |1 +--+ 28| VCC
| A12 |2 27| /WE
| A7 |3 26| A13----.
| A6 |4 25| A8 |
| A5 |5 24| A9 ---
| A4 |6 23| A11 -
| A3 |7 61256 22| /OE
| A2 |8 21| A10
| A1 |9 20| /CE
| A0 |10 19| D7
| D0 |11 18| D6
| D1 |12 17| D5
| D2 |13 16| D4
'--,-GND |14 15| D3
| +--------------+
---
-
The modifications are:
SRAM pin 1 (old N.C.) must be tied to ground
SRAM pin 26 (old CS2) must be tied to ground and the connection to Cart
Connector Pin 6 (A12) must be removed
74HC14 pin 1 must be connected to Cart Connector Pin 6. The resistor and
the +5V connection must be removed.
The rest remains equal.
> Thanks!
>
> Ian Primus
> ian.primus@xxxxxxx
>
> Maximiliam Luppe wrote:
>
> > I lost the instructions about programming. The first three chips in the
-
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