Hi,
I am trying to build a SNES card based on 1 27C322, 2 74xx257 and only one 74LS139.
Here's a picture:
http://imageshack.us/photo/my-images/11/61748144.jpg/
I have an 1J3B-01 4MB Hirom board with an 74ls139 as Sram decoder and 64k Sram.
This is how its connected by Nintendo.
How do I have to connect the 74LS139 when using 27C322 with 2 74xx257?
I really don't want to use an Mad-1 or a second 74ls139 as decoder.
Regards,
Michael
I am trying to build a SNES card based on 1 27C322, 2 74xx257 and only one 74LS139.
Here's a picture:
http://imageshack.us/photo/my-images/11/61748144.jpg/
I have an 1J3B-01 4MB Hirom board with an 74ls139 as Sram decoder and 64k Sram.
This is how its connected by Nintendo.
Code:
A15 1 16 VCC
A13 2 15 Pin 7 of 74LS139
A14 3 14 A21
NC 4 13 A22
NC 5 12 NC
NC 6 11 SRAM Pin 20=/CE
Pin15 7 10 NC
GND 8 09 GND
A13 2 15 Pin 7 of 74LS139
A14 3 14 A21
NC 4 13 A22
NC 5 12 NC
NC 6 11 SRAM Pin 20=/CE
Pin15 7 10 NC
GND 8 09 GND
How do I have to connect the 74LS139 when using 27C322 with 2 74xx257?
I really don't want to use an Mad-1 or a second 74ls139 as decoder.
Regards,
Michael