9 replies to this topic

[Tickled_Pink]

Been looking at the EPROMr project on the net for some time now. One of the problems with creating my own EPROM burner is the extra circuitry needed to supply the programming voltage ... however ...

I have a few EEPROMS here (as well as a pile of EPROMS) with a single 5v supply for both power and programming. This would make programming the devices much easier but I have one question: What, if any problems might I encounter if I try using an EEPROM instead of an EPROM for projects in the 8-bit Atari?

I know that EEPROMS have generally slower access times. Might that cause a problem?

[Thelen]

What kind of eeprom is it ? not a serial one ? :wink: It will work, but how many ns is the acces time of an eeprom and a epprom ? When the atari won't get it's data within a certain time, it will hang....

Thelen

[Tickled_Pink]

I think the best thing for me to do is to try it out on something

The EEPROMS are new ones manufactured by a company called Catalyst. I think most EPROMs operate within the 70ns - 150ns range. These particular EEPROMs operate at around 200ns. I also have some Flash ROMs from the same company and they operate at under 120ns ... but need a 12v programming pulse, which makes a programmer slightly more complicated.

I did design a simple EEPROM programmer for the 8-bit a few months ago but since lost the schematics. Never got around to building the thing. It operated off the joystick ports which transmitted control information to the 'board' serially and received the information serially from a parallel EEPROM.

[Thelen]

I don't think it's difficult to get a 12V programming pulse ? just use a 7812 regultor, and you can use a thryristor to switch it on or off ?

over the years I've built lot's of things, sort of eprom programmers too, but a little more specialized, Ram cartridge programmers fot the atari 2600 and atari 8 bit

Thelen

[Tickled_Pink]

I was thinking more along the lines of using a DC/DC converter or charge pump IC?

[Thelen]

a dc->dc converter is a regulator, when having a DC voltage of 18V, and connect it to a 7812 regulator, the output will be 12V......connect it to a 7805 regulator, you will have 5 volts as output.... but i don't really see the problem, when programming an 2732 eprom, 12V model, you can just connect the program voltage constant to VPP, Only when /CE is lowerd for the right programming time, the data will be put in the eprom.

thelen

[Tickled_Pink]

There shouldn't be a problem, I agree. The only 'problem' I had when designing the EEPROM programmer was making it all work with the limited number of pins on the Atari's joystick ports.

The idea behind everything was to make it as simple as possible by avoiding having to add any control lines for the programming voltage. Initially, I had hoped to use something like a charge pump which would increase the voltage from the +5v on the joystick ports. Got a couple somewhere, I think. The DC to DC converters I was thinking of are the step-up converters, rather than the step-down regulators.

Another possibility which I've yet to look at is using an I/O expander chip. I've got some MAXIM 7300 chips which are quite impressive and give you 20 I/O pins. With this I'd only need to use two pins on a joystick port for both input and output (well, one pin to be exact - the other would be used as a clock signal), thereby leaving me with 6 other pins for additional control logic if need be (or add 3 more 7300 chips for one helluva hardware controller with 80 I/O pins!! ).

The only problem I can think of with this approach (i.e. getting the Atari to supply all the voltages to the programmer) of trying to avoid having to use an external power supply is that, whichever method I choose, there probably wouldn't be enough supply current to the EPROM - so I'd probably need an external PSU anyway.

[Thelen]

ah, now is see, you want to make an eprom programmer for the atari 8 bit :wink: I was thinking it was for a pc :wink:

The programming voltage is indeed a problem....and the pins on the joystic port too. Now i'm thinking about that, why not make some kind of cartridge that can program eproms ?

Thelen

[CPUWIZ]

You would have the same problem, the cart slot only delivers 5V AFAIK.

[Tickled_Pink]

The Super EBurner from CSS programmed EPROMs from the cart slot but I think it also needed an external power supply to provide the additional voltages.