Reading Roms from an Apple II

[bibilit]

Another post related to clones.
What is the way to read 2316 Roms ?

using a 2716 instead of a 2316 is easy to find, but the other way round is misleading.
I will like to read my clone Roms for safety purposes.

 

[Skate323k137]

Good on you for dumping them; I have seen it done with a breadboard circuit and consumer programmer:

Testing Apple II Europlus ROMs

As part of my repair series on the Europlus, the next step I'm taking to investigate the "screen full of question marks" is to ensure the...

www.dmcmillan.co.uk

 

[bibilit]

Yes, seen that one but this is the misleading i was speaking about.

 

[Skate323k137]

Can you try to clarify what you may not be understanding? That method should allow you to dump the data.

I could see some confusion when it comes to burning another one; If you reprogrammed the data you obtained to a 2716, I believe that's when you would need an adapter to use it in circuit in place of a 2316.

 

[bibilit]

My understanding is that both pins 18 and 21 should be low instead of high.
Then, the site says that pin 20 (not 21) and 18 are connected to pin 8 and 9.
My understanding is that the 74LS04 will invert
the signal between pin 8 and 9, so high to low or the other way round.
So i am not sure if there’s a mystake with the pin 20 instead of pin 21, or if pin 21 should be connected to 8 and 18 to pin 9 (hence inversing signal from 21 to 18)

 

[bibilit]

Think i figured it out (with the help of a friend)

Pin 21 (CS3) should be connected to ground (pin 12 of the 2316 or 7 of the 74LS 04), the 2716 is connected to Vpp instead.

Pin 20 is connected to the input 74LS04 and output is connected to pin 18 (so receiving an inverted signal)

VCC and Ground are tied together between the 2316 and 74LS04

 

[VeryVon]

I recently went through this special sort of breadboarding hell to diagnose an Apple][+ rom set I'm sure there's a better way, but this is my first time so I figured it would be a good learning exercise.

The "Testing Apple II Europlus ROMs" article is a good start, and I agree with the OP that it's a tiny bit fuzzy. To clear things up a bit:

1. According to "The Apple II Circuit Description" CS3 should be LOW, so tie it to ground
2. CS2 is active HIGH, so we use an inverter to drive it via CS1
3. Connect all pins except 18 & 21 to the reader 1-1
4. Now preset your eprom reader to a 2716 and read away...

Here's the rig that ended up working for me:


p.s. Bonus info, I found a tasty link here discussing apple ROMS. In a plot twist, the Apple Character ROM reads 1-1 as a 2716 without any trickery!

p.p.s. All my ROMS were good except for F0 which appears to be DOA. Now how to replace it is my next adventure. The link above may be the key …

 

[tony359]

I know this is an old thread but thanks for this! I struggled for a while because as said the original article has typos in it.
Also it wasn't clear that pin 20 is tied to the programmer AND to the inverter which is then driving 21 which is NOT tied to the programmer.

I've finally got a reading. Why aren't the developers of the T48/T866II adding this IC? Grrr!

Thanks!

 

[bibilit]

I managed to build a socket adaptor for testing purposes (ugly but works)

Using a known bad Rom, it was read ok and comparing it with a good rom .bin image, i know now for sure is bad.