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SNES /RD strobe width (ns)?
http://forums.nesdev.com/viewtopic.php?f=12&t=10463
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Author:  bazz [ Thu Sep 05, 2013 9:30 pm ]
Post subject:  SNES /RD strobe width (ns)?

Hello,

In order to place the correct peripheral onto my snes cartridge, I must match the timing. What is the /RD strobe width in nanoseconds on SNES->Cart reads?

Regardless if the answer already exists, how would I have discovered this independently?

Thanks for your answers,
bazz

Author:  bazz [ Thu Sep 05, 2013 9:34 pm ]
Post subject:  Re: SNES /RD strobe width (ns)?

Also, the Read Cycle Delay is important.

Author:  bazz [ Thu Sep 05, 2013 9:53 pm ]
Post subject:  Re: SNES /RD strobe width (ns)?

I imagine someone might mention oscilloscope. I have never used one. Maybe my college physics department has one *_*

Author:  qwertymodo [ Thu Sep 05, 2013 10:40 pm ]
Post subject:  Re: SNES /RD strobe width (ns)?

bazz wrote:
I imagine someone might mention oscilloscope. I have never used one. Maybe my college physics department has one *_*

The EE department is more likely, if your school has one.

Also, the /RD strobe timing isn't really the important measurement when considering component selection, it's the amount of time between initiating a read and actually reading the data that you care about. SlowROM is 200ns, FastROM is 120ns. This is the maximum amount of time after the SNES read request (I believe that this corresponds with the falling edge of the /RD signal, but someone correct me if I'm wrong) and the expectation that the data is valid. This is why the -120 speed grade AM29F032B's are used, because they are fast enough for both SlowROM and FastROM games.

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