4 ms·

I'm not exactly sure about the Master System [1], but many systems of the time send an 8 bit vector at 60 Hz to indicate what buttons were pressed. Each bit rep

by bane 5y ago

I'm not exactly sure about the Master System [1], but many systems of the time send an 8 bit vector at 60 Hz to indicate what buttons were pressed. Each bit represents some action on the system e.g. bit 0 - up bit 1 - left bit 2 - right bit 3 - down bit 4 - button 1 bit 5 - button 2 bit 6 - start bit 7 - select This means that it was fairly easy to do some simple bit twiddling to read what buttons were pressed and what wasn't. Example: left+up+button 1 would produce a vector like: 11001000 1 - The bit layout is here under "Joypad Ports" and it's actually kind of interesting and a bit more complex than my simple example, but the method is the same. https://www.chibiakumas.com/z80/MasterSystemGameGear.php https://www.chibiakumas.com/z80/MasterSystemGameGear.php It looks like they maybe could have fit extra buttons in under the third port (&00) but never did. It's likely they tried to maintain backwards compatibility with previous systems like the SG-1000, only adding something new when the Gamegear came out. Here's some more on how the NES handles this http://www1.cs.columbia.edu/~sedwards/classes/2007/4840/reports/TupacMan.pdf http://www1.cs.columbia.edu/~sedwards/classes/2007/4840/repo...

LAC-Tech 5y ago
That makes sense - but why was that abandoned in the 16 bit era? Neither the sega megadrive nor the super nintendo have 16 inputs.
- fredoralive 5y ago
  SMS wires each button to a seperate pin on the connector in a variant on the Atari style controller port. Megadrive has a Master System backwards compatability mode (and the same 9 pin port), so its controller ports are going to be similar 8 bit IO ports. It adds extra buttons using a spare line as a select / multiplex output and reading the input lines multiple times. Nintendo used shift regiters in its controllers, and the SNES does use a 16 bit shift register, but some of the bits are unused (4 extra buttons deemed sufficient it seems).
Nition 5y ago
For the record, you could plug a Sega Genesis controller into a Master System and it worked (at least with the games I had) despite having more buttons. The B and C buttons became the main two buttons.
- city41 5y ago
  There's about ten games that require a SMS controller to work.
crtasm 5y ago
There was only a D-pad and two buttons on the Master System, no Start or Select. The console itself had a single 'pause' button that I suppose might have been wired into the joystick circuit though.

by bane 5y ago

LAC-Tech 5y ago

That makes sense - but why was that abandoned in the 16 bit era? Neither the sega megadrive nor the super nintendo have 16 inputs.

fredoralive 5y ago
SMS wires each button to a seperate pin on the connector in a variant on the Atari style controller port. Megadrive has a Master System backwards compatability mode (and the same 9 pin port), so its controller ports are going to be similar 8 bit IO ports. It adds extra buttons using a spare line as a select / multiplex output and reading the input lines multiple times. Nintendo used shift regiters in its controllers, and the SNES does use a 16 bit shift register, but some of the bits are unused (4 extra buttons deemed sufficient it seems).

Nition 5y ago

For the record, you could plug a Sega Genesis controller into a Master System and it worked (at least with the games I had) despite having more buttons. The B and C buttons became the main two buttons.

city41 5y ago
There's about ten games that require a SMS controller to work.

crtasm 5y ago

There was only a D-pad and two buttons on the Master System, no Start or Select. The console itself had a single 'pause' button that I suppose might have been wired into the joystick circuit though.