Why does the Apple ][ have a hardware-encoded keyboard?

From: Allison J Parent <allisonp_at_world.std.com>
Date: Sat May 30 20:27:23 1998

<That I'd heard before, which is why I'm so supprised by the
<hardware-encoded keyboard in an otherwise software-driven machine.

Things you cant do with a software scanned keyboard:

 Key pressed interrupt, if the cpu doesn't scan the keyboard it cannot
 sense activity. It takes some chips extra then to sense any key pressed
 and cause a interupt to initiate a keybard scan and debounce routine
 to see what happend.

 The keyboard chips did n-key rollover and buffered at least one
 keystroke.

 Fewer signal carrying wires in the air, the keyboard encoders were slow
 and didn't create much RFI, scan lines off the bus or a port can be quite
 noisy.


 Allison
Received on Sat May 30 1998 - 20:27:23 BST