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| 6800 Address Decoding http://anycpu.org/forum/viewtopic.php?f=17&t=81 |
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| Author: | James_Parsons [ Wed Sep 04, 2013 12:44 pm ] |
| Post subject: | 6800 Address Decoding |
Hello. Some May know Me From The 6502 Forum. I am Currently Working On A 6800 Computer, And I Need Help With Address Decoding. I Am Having Trouble Comprehending The Articles And PDFs I Find On Google. I Have Done Research, Im Just Having Trouble. Can Someone Dumb This Topic Down For Me. Im Using: Two 6821 PIA One 64x8 ROM One 32x8 RAM |
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| Author: | Garth [ Wed Sep 04, 2013 7:07 pm ] |
| Post subject: | Re: 6800 Address Decoding |
I have looked at the 6800 in the past but never used it. I know it is very, very similar to the 6502, and I was just looking back at my address-decoding page in the 6502 primer to see if there would be something to help you, but I guess now I have to ask for more specifics. What parts seem the most mysterious? I'm wondering about your RAM and ROM sizes too. I assume you mean 64Kx8 (like a 27c512) ROMs and 32Kx8 RAM (like a 62256); but the 6800 has a memory map of 64KB, so you cannot get 160KB of memory, plus I/O in that space, unless you do some sort of banking arrangement with external hardware. A beginner definitely won't be using that much memory anyway. |
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| Author: | James_Parsons [ Thu Sep 05, 2013 12:47 pm ] |
| Post subject: | Re: 6800 Address Decoding |
I am reviving that memory problem. I now have decided 16kx4 ROM and 16kx4 RAM. The rest of thememory is for I/O |
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| Author: | Garth [ Thu Sep 05, 2013 8:02 pm ] |
| Post subject: | Re: 6800 Address Decoding |
16Kx4?? Where will you find that? 16Kx8 is a standard size for ROM. To get 16Kx8 RAM, you just use a 32Kx8 (since there's no 16Kx8) and one address pin doesn't get used the normal way. |
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