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  • Joined: 25 Feb 2013
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Detecting if it's a game gear
Post Posted: Tue Mar 20, 2018 9:15 am
As the titles says, is there a way to detect whether the code is running on the gamegear?
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  • Joined: 05 Sep 2013
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Post Posted: Tue Mar 20, 2018 9:30 am
you mean you want your code to run both on SMS and on Game Gear and be able to tell the difference?
I guess it's not possible by querying the VDP - maybe querying port $00 - but I don't know what it returns on SMS... :|
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Post Posted: Tue Mar 20, 2018 9:53 am
yes, I want to run my code on both of them, and do different things depending on what it's running on. Is port 00 readable?

https://github.com/oboroc/sms-journey/blob/master/doc/smstech.txt

states the initial values, but not whether they can be read or not
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Post Posted: Tue Mar 20, 2018 10:02 am
yes, in Game Gear mode, the msb at port $00 gives you the state of the START key (0=pressed, 1=not!)

note that the Game Gear can also run in SMS mode, you probably don't want that.
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Post Posted: Sun Mar 25, 2018 8:16 am
I spotted a bit on this discussion that talks about detection. Scroll down a post or two and youll find it.

http://www.smspower.org/forums/15019-KrisalisSoftwareSMSGGDevBox#82986
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Post Posted: Sun Mar 25, 2018 9:15 am
Avoiding to Charles' doc, port $00 reads return:

SMS: the last byte of the instruction which read the port.
SMS 2, GG (SMS mode), Genesis with PBC: $FF.
GG (GG mode): Start button and region information
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Post Posted: Mon Mar 26, 2018 3:45 am
thank you everybody!
I didn't know that start must be polled. Does this mean that start does NOT correspond to an NMI?
is the hardware NMI line disabled when in game gear mode?
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Post Posted: Mon Mar 26, 2018 6:41 am
In GG mode, NMIs are used for Gear to Gear, to signal when data is received.
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Post Posted: Tue Mar 27, 2018 11:06 pm
I didn't know that, that is interesting!
how is the data sent retrieved / is there any documentation abot the gear to gear?
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Post Posted: Tue Mar 27, 2018 11:55 pm
Yes, it's well documented but not well emulated. There is hardware handshaking so basically each system can send a byte to the other and then the recipient gets an NMI and has to read it out immediately as there's no buffering. The software then makes a protocol on top of that.
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Post Posted: Wed Mar 28, 2018 7:51 am
Do you have any reference?
(I found that retrocopy emulates it)
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Post Posted: Wed Mar 28, 2018 8:25 am
http://www.smspower.org/Development/GearToGearCable

Retrocopy is a weird emulator...
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Post Posted: Thu Mar 29, 2018 2:37 am
thank you, I evidently didn't search enough
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Detecting if it's a game gear
Post Posted: Fri Nov 02, 2018 9:05 am
The Game Gear had a much more impressive library, about five times the Lynx's (not including Master System games). Many Lynx games are far more impressive than Game Gear games, though; I think the Lynx would easily outclass the Game Gear if it had survived for another two years.
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Post Posted: Sun Nov 04, 2018 4:51 pm
Port 0 does indeed work for GG vs SMS (and GG vs. GG-SMS); if it's instead GG-SMS mode you're trying to distinguish from an actual SMS, this is trickier but sverx figured it out and implemented it in the test suite; see http://www.smspower.org/forums/17116-SMSTestSuiteWorkInProgressHomebrew?start=10... for discussion and downloads.
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Post Posted: Mon Nov 05, 2018 8:58 am
Thank you!!
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