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The controller ports have a TH line, which is can be used as an output on the Western SMS. AFAIK this should allow e.g. the use of 3 buttons on Sega Genesis controllers.

On the SC-3000 and the SC-1000 Mark II and Mark III, the TH line is connected to GND (on the original SC-1000 it is unconnected). And the documentation at http://www.smspower.org/Development/PeripheralPorts about I/O control port 0x3f "This functionality is not present on the Mark III and Japanese Master System. As a result, it is commonly used for region detection. It also means that for compatibility, it defaults to an input-only state (ie. with all the low bits set) on startup."

But according to the schematic at http://www.smspower.org/forums/files/master_system__jap_fm_786.png, the TH line is connected in the Japanese Master System. And there is a resistor in the line, just like TR, but no other pins. I assume the resistor is for the protection of an input, which indicates that it could be possible to use TH and TR as inpuits, like on the Western SMS.

Is there any additional information available on the Japanese SMS controller ports?

Philipp

I posted about it here:

http://www.smspower.org/forums/15878SG1000IISEGAMARKIIIAndJAPSMSSchematic

But I should probably write a proper document about it. To summarize:

TH has a simpler implementation compared to the US SMS. When TH is configured as an input it is pulled high by an internal pull-up resistor . When TH is configured as an output it drives low.

Unlike the US SMS there is no dedicated control to set the output level. So you have to set them as inputs to make them high and outputs to make them low.

About reading back the TH pin state, when they are inputs you read back the level of whatever is attached to the TH pin. When they are outputs they always return zero.

Author	Message
PkK Joined: 07 Aug 2007 Posts: 220 Location: Yach, Germany	How does TH work on the japanese SMS? Posted: Mon Feb 20, 2017 7:48 am
	The controller ports have a TH line, which is can be used as an output on the Western SMS. AFAIK this should allow e.g. the use of 3 buttons on Sega Genesis controllers. On the SC-3000 and the SC-1000 Mark II and Mark III, the TH line is connected to GND (on the original SC-1000 it is unconnected). And the documentation at http://www.smspower.org/Development/PeripheralPorts about I/O control port 0x3f "This functionality is not present on the Mark III and Japanese Master System. As a result, it is commonly used for region detection. It also means that for compatibility, it defaults to an input-only state (ie. with all the low bits set) on startup." But according to the schematic at http://www.smspower.org/forums/files/master_system__jap_fm_786.png, the TH line is connected in the Japanese Master System. And there is a resistor in the line, just like TR, but no other pins. I assume the resistor is for the protection of an input, which indicates that it could be possible to use TH and TR as inpuits, like on the Western SMS. Is there any additional information available on the Japanese SMS controller ports? Philipp

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Mon Feb 20, 2017 9:40 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	I posted about it here: http://www.smspower.org/forums/15878SG1000IISEGAMARKIIIAndJAPSMSSchematic But I should probably write a proper document about it. To summarize: TH has a simpler implementation compared to the US SMS. When TH is configured as an input it is pulled high by an internal pull-up resistor . When TH is configured as an output it drives low. Unlike the US SMS there is no dedicated control to set the output level. So you have to set them as inputs to make them high and outputs to make them low. About reading back the TH pin state, when they are inputs you read back the level of whatever is attached to the TH pin. When they are outputs they always return zero.

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