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  • Joined: 25 Feb 2013
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Game gear cartridges in SMS mode
Post Posted: Wed Nov 03, 2021 8:02 am
Do cards that use SMS mode connect the GG pin to VCC or do they leave it floating?
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  • Joined: 04 Jul 2010
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Post Posted: Wed Nov 03, 2021 8:06 am
floating pin is the worst possible idea ^^
As the level is indeterminate ;)
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Post Posted: Wed Nov 03, 2021 8:41 am
There may be a pull up inside the GG.
If you have a look at Mark III cartridges, those who use the glasses leave the CSCN4 pin unconnected to not disable the cart port.
I think the definitive answer would come only from a pic of an actual cartridge in SMS mode (mickey?)
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Post Posted: Wed Nov 03, 2021 9:26 am
Last edited by ichigobankai on Thu Nov 04, 2021 10:05 am; edited 1 time in total
the pin on the IC seems to be an input pin
Labelled /GG (gg mode = gnd) on IC pinout.
(can see some components ; Qx and Rx on schematics)

edit. Briefly tested on my 2 asics the pin is held at ~4v (without cartridge) which can explain why GG pcb are forced to GND

for Mickey, it must be the Castle of Illusion, not Land.
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Post Posted: Wed Nov 03, 2021 2:25 pm
Thank you! There must be a pull up then.
Do you have Castle of Illusion,as to check what original cartridges did?
I tried to make a "repro" cart, but as I wrote in another post, I get flickering. I do not know if it's my fault or if that's the norm for sms mode.
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Post Posted: Thu Nov 04, 2021 5:43 am
Would a gear master converter be helpful? As thats esentially doing the same thing?
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Post Posted: Thu Nov 04, 2021 7:19 am
Just popped open a gear master... its just floating, so one would assume its likely the same for games that run in sms mode. The /tv pin is tied to +5v though.. have you done that on your board?
20211104_200942.jpg (221.21 KB)
20211104_200942.jpg

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Post Posted: Thu Nov 04, 2021 10:08 am
I can test if it runs SMS game without forcing a state, as i've made few GG boards.

But based on what i've found and your gear master pcb, the GG seems to be on SMS mode by default (which is funny).
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Post Posted: Fri Nov 05, 2021 3:56 am
Thank you guys

wasup wrote
The /tv pin is tied to +5v though.. have you done that on your board?


Yes, all (game gear mode) commercial carts I have do that as well, so I copied it.
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Post Posted: Sun Nov 07, 2021 1:00 pm
ichigobankai wrote
the pin on the IC seems to be an input pin
Labelled /GG (gg mode = gnd) on IC pinout.
(can see some components ; Qx and Rx on schematics)


Indeed, the GG pin is connected to R23, a pull up to +5V.
And yes, how funny that the "default" mode is SMS mode :D
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