Version Register

Ask anything your want about Megadrive/Genesis programming.

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mickagame
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Version Register

Post by mickagame » Mon Feb 15, 2021 7:05 pm

The version register in IO Chip give informations like :

Bit(7) : Mode => Pin /LANG from IO Chip (can be set by jumper)
Bit(6) : VMode => Pin /PAL from IO Chip (can be set by jumper)
Bit(5) : Disk => Pin /DISK from IO Chip
Bit(4) : Reserved
Bit(3-0) : Version => ???

Is there any signal from IOChip corresponding to Bit(3-0) or value are stored inside the chip?

TmEE co.(TM)
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Re: Version Register

Post by TmEE co.(TM) » Mon Feb 15, 2021 7:46 pm

Verison part is hardwired to 0001 on all hardware I have seen (that has TMSS)
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Mask of Destiny
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Re: Version Register

Post by Mask of Destiny » Mon Feb 15, 2021 11:00 pm

Yeah, it's zero on a 315-5309 IO chip and 1 on the 315-5402 (integrated IO chip and arbiter on a VA5) and all later IO chip versions. The 315-5402 doesn't have a full TMSS implementation though. Attempting to bank in the TMSS ROM will lock the machine (assuming because !DTACK is not being asserted for that address)

mickagame
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Re: Version Register

Post by mickagame » Tue Feb 16, 2021 11:47 am

Ok thanks for this informations :-)
The value is hardwired inside the chip or come from external (by a jumper for example)?

TmEE co.(TM)
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Re: Version Register

Post by TmEE co.(TM) » Tue Feb 16, 2021 11:48 am

Right, 315-5402 is special, it shows no TMSS when in JP mode, while TMSS is shown in EN mode. I did notice the freezing problem with TMSS as I tried to dump the ROM when accessing the banking register...

The value is not adjustable externally.
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Mask of Destiny
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Re: Version Register

Post by Mask of Destiny » Tue Feb 16, 2021 6:25 pm

TmEE co.(TM) wrote:
Tue Feb 16, 2021 11:48 am
Right, 315-5402 is special, it shows no TMSS when in JP mode, while TMSS is shown in EN mode. I did notice the freezing problem with TMSS as I tried to dump the ROM when accessing the banking register...
Interesting. Were systems with the 315-5402 were actually released outside of Japan, or is this just from testing Japanese units with a region mod?

TmEE co.(TM)
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Re: Version Register

Post by TmEE co.(TM) » Tue Feb 16, 2021 7:53 pm

I have only ever seen the chip in Japanese machines, never in EU or US ones. I have the chip transplanted onto an EU VA5/6 board and the region mod changes TMSS behaviour. l_oliveira has some observations done too in past, telling that "SEGA" write is unnecessary when the language setting is in JP instead of EN (50/60 has no effect).
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