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I tried to use the same diagram with not swapped bins (.SMC EPROM). I just tied pin1 (A19) of M27C801 to Data Out 2 But it doesn't work. It's work only with swapped method . Whats wrong? If it's always A19, why its dont work anymore ? https://i2.imageban.ru/out/2020/08/27/5960207019861715449f5e51853...

I found that some custom PCB use different connections. M27C801 pin 24 (/OE) -----> Cartridge connector pin 23 (/RD) M27C801 pin 24 (/OE) -----> Cartridge connector pin 49 (/OE) I am confuse. Why so? Nintendo released PCBs with both layouts. Pedantically, only the former is correct. A lot of people...

Hello again, When no swapbinning , I found that some custom PCB use different connections. M27C801 pin 24 (/OE) -----> Cartridge connector pin 23 (/RD) M27C801 pin 24 (/OE) -----> Cartridge connector pin 49 (/OE) I'am confuse. Why so? For me the second one is the right one. Why connect to pin 23 (/R...

You think about it. I explain how decoders work in that post. If you can understand how everything works on the board you'll be able to troubleshoot things like this a lot easier, instead of just relying on a table. Thank you, I always go back to you page explainer when I try to understand some thi...

poorstudenthobbyist wrote: ↑Wed Sep 09, 2020 12:41 pm ...What happens to the output of the decoder when you switch A13 and A14?

How can I see what happens?

I still confuse. I found that I probably made some mistakes on my circuit for SRAM decoder 74HC139. if I compare with poorstudenthobbyist https://thepoorstudenthobbyist.com/2019/05/18/custom-pcb-explanation/#memorymap https://i2.imageban.ru/out/2020/09/03/04526e73f99cdf62863991aebbcce500.png Pin2 (1...

Strange, strange... I tried to make on same board some saves of games. I take « Mario All stars » LoROM game (64kb RAM). ROM files was also expanded to 27C322 EPROM. When i take of and put it again, i see file name created. So its holds Data inside. But when I load game with this file, Game starts f...

I use HM62 64 ALP-10 Then I tested with HM62 256 ALP-10. This schematic is only for a 64 kibit RAM. It will not work with a 256 kibit RAM: pin 26 became an address line, no longer an enable. For a 256 kibit RAM, you must use a schematic that gently pulls pin 20 high when power is removed. I found m...

poorstudenthobbyist wrote: ↑Wed Sep 02, 2020 5:48 pm Do you have both 139s in the board?

No.
I put only one,
and solder jumpers for LoROM decoder

What does your circuit on pin 20 look like? What's your battery voltage? Battery alone = 2.959v Here is circuit of SRAM decoder where pin 20 of SRAM (/RAM_OE) are connected : https://i2.imageban.ru/out/2020/09/03/04526e73f99cdf62863991aebbcce500.png and here is SRAM jumpers to chose size of SRAM: h...

lidnariq wrote: ↑Wed Sep 02, 2020 4:43 pm What does a voltmeter say pins 28, 26, and 20 are doing when power is removed?

pin 20 = 0.002v
pins 26= 0v
pins 28 = 2.405v

lidnariq wrote: ↑Wed Sep 02, 2020 4:28 pm ... what? No, +CE should be low during retention, and high during operation. And the 2N2222 fragment should already do that.

OMG ...

I already test it and its not works.

So I dont understand why its not working.
DO you have any idea?
Please lidnariq

krzysiobal wrote: ↑Wed Sep 02, 2020 4:10 pm Pin26 of SRAM needs to be HIGH when in batterry retention mode - pull it up to pin 28 with 100k resistor..

Like that ?

Hi, Can you help me please. I dont understand why my SRAM are not holding saves of games? The game that I test is Legend of "Zelda, The - A Link to the Past" (64 SRAM). File was expanded to 27C322 EPROM. I use HM6264ALP-10 https://ae01.alicdn.com/kf/Had8bfb1fbecc49cdbc9a44777749926bm/Frees...

lidnariq wrote: ↑Wed Sep 02, 2020 10:02 am Those numbers are measured in nanoseconds from when the CPU changes the address, or asserts /CE, to when the output is guaranteed valid.

With the sole exception of maybe the PC Engine, both of these speeds should be fine for every 5V console I can think of.

thanks