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kscanfast.c
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kscanfast.c
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// Fast keyboard scan for the TI-99/4A by Tursi aka Mike Brent
// This code and library released into the Public Domain
// You can copy this file and use it at will ;)
#include "kscan.h"
// By columns, then rows. 8 Rows per column. No shift states
const unsigned char keymap[] = {
61,32,13,255,1,2,3,255,
'.','L','O','9','2','S','W','X',
',','K','I','8','3','D','E','C',
'M','J','U','7','4','F','R','V',
'N','H','Y','6','5','G','T','B',
'/',';','P','0','1','A','Q','Z'
};
void kscanfast(int mode) {
if (mode == 0) {
KSCAN_KEY = 0xff;
for (unsigned int col=0; col < 0x0600; col += 0x0100) {
unsigned int key;
__asm__("li r12,>0024\n\tldcr %1,3\n\tsrc r12,7\n\tli r12,>0006\n\tclr %0\n\tstcr %0,8" : "=r"(key) : "r"(col) : "r12"); // set cru, column, delay, read
unsigned int shift=0x8000;
for (int cnt=7; cnt>=0; cnt--) {
// a pressed key returns a 0 bit
if (key & shift) {
shift>>=1;
continue;
}
// found one
KSCAN_KEY = keymap[(col>>5)+cnt];
return;
}
}
} else {
unsigned int key;
int col = 0x0600; // joystick 1 fire column
if (mode == 2) {
col = 0x0700; // make that joystick 2
}
__asm__("li r12,>0024\n\tldcr %1,3\n\tsrc r12,7\n\tli r12,>0006\n\tclr %0\n\tstcr %0,1" : "=r"(key) : "r"(col) : "r12"); // set cru, column, delay, read (only need 1 bit)
if (key == 0) {
KSCAN_KEY = 18;
} else {
KSCAN_KEY = 0xff;
}
}
}