Keyboard Reading

sandruzzo · 21 February 2019, 16:59

Is it possible to read KeyBoard whitout using interrupt vbr?

phx · 21 February 2019, 17:08

VBR? That's the Vector Base Register. You probably mean VBL, but even that would be wrong. Keyboard interrupts are generated at CIA-A, which then assigns the level-2 interrupt line.

You can read keycodes and do the handshaking without establishing a level-2 interrupt handler, of course. Just poll the CIA-A ICR register and wait for the next SP interrupt. Then read the CIA's serial port data register for the keycode and do the handshaking afterwards.

sandruzzo · 21 February 2019, 17:09

Quote:

Originally Posted by phx

VBR? That's the Vector Base Register. You probably mean VBL, but even that would be wrong. Keyboard interrupts are generated at CIA-A, which then assigns the level-2 interrupt line.

You can read keycodes and do the handshaking without establishing a level-2 interrupt handler, of course. Just poll the CIA-A ICR register and wait for the next SP interrupt. Then read the CIA's serial port data register for the keycode and do the handshaking afterwards.

Thanks. I'm very bad on that stuff!

Photon · 14 March 2019, 00:26

If you handshake, process more than one keypress per frame to avoid buffering lag. You can also check for each specific key used without using interrupts. This works fine even on the bastard in the cabbage patch, the infamous Cherry-branded A2000 keyboard.

21 February 2019, 16:59	#1
sandruzzo Registered User Join Date: Feb 2011 Location: Italy/Rome Posts: 2,281	Keyboard Reading Is it possible to read KeyBoard whitout using interrupt vbr?

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21 February 2019, 17:08	#2
phx Natteravn Join Date: Nov 2009 Location: Herford / Germany Posts: 2,496	VBR? That's the Vector Base Register. You probably mean VBL, but even that would be wrong. Keyboard interrupts are generated at CIA-A, which then assigns the level-2 interrupt line. You can read keycodes and do the handshaking without establishing a level-2 interrupt handler, of course. Just poll the CIA-A ICR register and wait for the next SP interrupt. Then read the CIA's serial port data register for the keycode and do the handshaking afterwards.

14 March 2019, 00:26	#4
Photon Moderator Join Date: Nov 2004 Location: Eksjö / Sweden Posts: 5,602	If you handshake, process more than one keypress per frame to avoid buffering lag. You can also check for each specific key used without using interrupts. This works fine even on the bastard in the cabbage patch, the infamous Cherry-branded A2000 keyboard.

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