kscanfast.c

// keypad scan (neither fast nor slow in the Coleco version)
// This code and library released into the Public Domain
// You can copy this file and use it at will ;)

#include "kscan.h"

#define SELECT 0x2a

// fire buttons are all the same for the moment. Note that 2 and 3 read
// via the keypad, but 1 has a dedicated bit and could be overlapped
#define FIRE1 18
#define FIRE2 18
#define FIRE3 18

// note: keys index 8 and 4 are fire 2 and fire 3, respectively
// for now, I'm defining them the same as regular fire (18),
// but if I ever want to split up them, I can update this.
const unsigned char keys[16] = {
	0xff, '8', '4', '5', 
	0xff, '7', '#', '2',
	0xff, '*', '0', '9',
	'3',  '1', '6', 0xff
};
// FIRE 1 returns as bit 0x40 being low

static volatile __sfr __at 0xfc port0;
static volatile __sfr __at 0xff port1;
static volatile __sfr __at 0x80 port2;
static volatile __sfr __at 0xc0 port3;

// For Coleco, all modes except 2 read controller 1, and 2 reads controller 2
void kscanfast(unsigned char mode) {
	unsigned char key;

	port2 = SELECT;		// select keypad

	if (mode == KSCAN_MODE_RIGHT) {
		key = port1;
	} else {
		key = port0;
	}
	// bits: xFxxNNNN (F - active low fire, NNNN - index into above table)

	// if reading joystick, the fire button overrides
	// Note this limits us not to read keypad and fire at the same time,
	// which honestly I will probably want later.
	if ((key&0x40) == 0) {
		KSCAN_KEY = FIRE2;
	} else {
		KSCAN_KEY = keys[key & 0xf];
	}

	port3 = SELECT;		// select joystick
	if (mode == KSCAN_MODE_RIGHT) {
		key = port1;
	} else {
		key = port0;
	}
	// active low bits:
	// xFxxLDRU
	if ((key&0x40) == 0) {
		KSCAN_KEY = FIRE1;
	}

}