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As the titles says, is there a way to detect whether the code is running on the gamegear?

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... :|

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

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.

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

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

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?

In GG mode, NMIs are used for Gear to Gear, to signal when data is received.

I didn't know that, that is interesting!
how is the data sent retrieved / is there any documentation abot the gear to gear?

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.

Do you have any reference?
(I found that retrocopy emulates it)

http://www.smspower.org/Development/GearToGearCable

Retrocopy is a weird emulator...

thank you, I evidently didn't search enough

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.

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.

Thank you!!

Author	Message
kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	Detecting if it's a game gear 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?

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	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... :\|

kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	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

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	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.

wasup Joined: 05 Nov 2014 Posts: 435 Location: Auckland - NZ	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

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14740 Location: London	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

kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	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?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14740 Location: London	Posted: Mon Mar 26, 2018 6:41 am
	In GG mode, NMIs are used for Gear to Gear, to signal when data is received.

kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	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?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14740 Location: London	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.

kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	Posted: Wed Mar 28, 2018 7:51 am
	Do you have any reference? (I found that retrocopy emulates it)

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14740 Location: London	Posted: Wed Mar 28, 2018 8:25 am
	http://www.smspower.org/Development/GearToGearCable Retrocopy is a weird emulator...

kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	Posted: Thu Mar 29, 2018 2:37 am
	thank you, I evidently didn't search enough

nadhim Joined: 02 Nov 2018 Posts: 2 Location: Turkey	Detecting if it's a game gear Posted: Fri Nov 02, 2018 9:05 am
nadhim Joined: 02 Nov 2018 Posts: 2 Location: Turkey	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.

bsittler Joined: 22 Apr 2018 Posts: 530	Posted: Sun Nov 04, 2018 4:51 pm
bsittler Joined: 22 Apr 2018 Posts: 530	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.

kamillebidan Joined: 25 Feb 2013 Posts: 384 Location: Osaka	Posted: Mon Nov 05, 2018 8:58 am
	Thank you!!

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