: _prevstat [ PAD_MEM LITN ] ;
: _sel [ PAD_MEM 1+ LITN ] ;
: _next [ PAD_MEM 2+ LITN ] ;

( Put status for port A in register A. Bits, from MSB to LSB:
Start - A - C - B - Right - Left - Down - Up
Each bit is high when button is unpressed and low if button is
pressed. When no button is pressed, 0xff is returned.
This logic below is for the Genesis controller, which is modal.
TH is an output pin that swiches the meaning of TL and TR. When
TH is high (unselected), TL = Button B and TR = Button C. When
TH is low (selected), TL = Button A and TR = Start. )
