#1081 - velvetfr - Tue Jan 14, 2003 1:05 pm
Hi guys,
is anyone has any clue how to use the z80-like chip on the GBA ?
Thanks in advance for your replies ...
#1082 - Touchstone - Tue Jan 14, 2003 1:58 pm
Stick a GBC cart in there, I think that's the only way to access the z80. When the gba is running in gba mode the z80 is supposed to be unavailable.
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#1089 - Splam - Tue Jan 14, 2003 2:26 pm
Yup, theres a little notch on either the gba or gbc cart (can't remember which one has it) which sets a switch and when gba boots it tests that to see what state to run in. If its a gba cart there is no way to access the z80 as a (partially) different set of hardware is then used.
#1091 - lordmetroid - Tue Jan 14, 2003 2:53 pm
wouldn't one be able to add such a switch to a gba cart manually?
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Last edited by lordmetroid on Tue Jan 14, 2003 4:39 pm; edited 1 time in total
#1093 - Touchstone - Tue Jan 14, 2003 3:04 pm
The thing is you cant do both z80 and arm7 at the same time as they are mutually exclusive.
But what about rendering hardware? Is it possible for gbc games to access gba rendering hardware in some way? I think someone told be about a secret room in zelda: oracle of season that used the gba rendering hardware in some way.
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#1099 - Splam - Tue Jan 14, 2003 5:05 pm
That certainly sounds a lot more possible than gba using the z80. Not sure how the gbc hardware registers are mapped but as the audio hardware uses the same format on gba as gbc (other than directsound of course) they might be mapped straight to the gba ones. In that case a bit of "accidental" writing to wrong addresses might do some cool stuff :)
#1101 - velvetfr - Tue Jan 14, 2003 5:12 pm
Are there any schematics of the GBA board to check how the z80 and the ARM processor are linked to the other components to see really how it works ?
Thanks ...
#1115 - tepples - Tue Jan 14, 2003 7:51 pm
| velvetfr wrote: |
| Are there any schematics of the GBA board to check how the z80 and the ARM processor are linked to the other components |
No. The Z80, the ARM7TDMI, and several other components are on the same die. To obtain schematics, you'd have to open up the "AGB CPU" package.
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#1116 - tepples - Tue Jan 14, 2003 7:55 pm
| Touchstone wrote: |
| Is it possible for gbc games to access gba rendering hardware in some way? I think someone told be about a secret room in zelda: oracle of season |
It doesn't use the GBA's new graphics hardware. It's just a special store where some items are cheaper, that's all.
Zelda: Oracle detects GB vs. SGB vs. GBC vs. GBA by checking the contents of the CPU registers at startup. You could probably circumvent this check on the GBC with a Game Genie or something.
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#1800 - djmips - Thu Jan 23, 2003 9:59 am
| tepples wrote: |
| velvetfr wrote: | | Are there any schematics of the GBA board to check how the z80 and the ARM processor are linked to the other components |
No. The Z80, the ARM7TDMI, and several other components are on the same die. To obtain schematics, you'd have to open up the "AGB CPU" package. |
They may be on the same die, but it appears to be quite a brute force seperation between the two modes; with the mechanical switch and the voltages changing from 3.3V (GBA) to 5V (GBC).
It doesn't offer much hope to the idea that you could share resources.