Minimum EPROM speed for CV?

[CannibalCat]

Hi, was seeing odd artifacts with an EPROM emulator unit I'm using and was wondering if the speed of memory in it (read time) was a factor, the static RAM is at 70ns. I have a burned EPROM of the same code which has a speed of 45ns and works fine, is there a minimum access speed for the CV?

 

Thanks,

Rich

[PkK]

At the clock speed of the Z80 in the ColecoVision the memory should have an access time of 280 ns or faster. There might be an additional delay of a few ns due to some logic chips in the paths, so I'd recommend 250 ns or faster to be on the safe side.

 

Philipp

[+nanochess]

The old EPROM used are very slow, typically 200ns.

 

I suspect more of a RAM address setup problem. I've had the experience that if you keep CE set some RAM memories show transitory "trash" in reading. I would put CE and OE together.

 

Also if your RAM is fully CMOS maybe you would need pull up. But I don't remember if in inputs or outputs to account for TTL to CMOS different voltages for logical 1.

[CannibalCat]

The old EPROM used are very slow, typically 200ns.

 

I suspect more of a RAM address setup problem. I've had the experience that if you keep CE set some RAM memories show transitory "trash" in reading. I would put CE and OE together.

 

Also if your RAM is fully CMOS maybe you would need pull up. But I don't remember if in inputs or outputs to account for TTL to CMOS different voltages for logical 1.

 

nanochess... thank you, your advice pointed me in the right direction... problem solved!

[+nanochess]

 

nanochess... thank you, your advice pointed me in the right direction... problem solved!

 

Glad to be of help