Apple II Plus Character Generator

3 replies [Last post]
Offline
Joined: Oct 21 2011
Posts: 4

If I wanted to see exactly the bit pattern for each of the 64 characters in the Apple II Plus character set, is there a place in memory (either RAM or ROM) I could look at (using the Monitor) to see the actual bit pattern for each character? Or is this information kept in the character generator chip itself and is not accessible through the 64KB memory addressing of the main computer?

I realize the character set is simple enough to figure out probably by just looking at the screen, but I'm more interested in how it works internally, and whether this information is available through the Monitor.

Thanks.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
Offline
Joined: Jun 5 2008
Posts: 380
Re: Apple II Plus Character Generator

The short answer is that the character rom is not readable by the processor.

The data sheet for the GI 2513 (used until the rev 7 version motherboard) can be found here and it may help answer your questions.

http://www.datasheetarchive.com/dl/Databooks-1/Book241-553.pdf

Regards,
Mike Willegal

Offline
Joined: Oct 21 2011
Posts: 4
Re: Apple II Plus Character Generator

Thanks, that does help a lot. Do you know what chip was used in rev 7 boards and later?

amauget's picture
Offline
Joined: Jan 3 2011
Posts: 242
Re: Apple II Plus Character Generator

Hello,

You can find this information (ans many others !) in Understanding the Apple II.
See chapter 8, pages 211-213
The ROM used by Apple in Rev 7 and later, 2316, was 2716 compatible.

__________________

Antony
Apple II forever