68 lines
1.7 KiB
C
68 lines
1.7 KiB
C
/*
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* ----------------------------------------------------------------------------
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* "THE BEER-WARE LICENSE" (Revision 42):
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* Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain
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* this notice you can do whatever you want with this stuff. If we meet some day,
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* and you think this stuff is worth it, you can buy me a beer in return.
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* ----------------------------------------------------------------------------
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include <time.h>
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typedef struct {
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int lastClkVal;
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int pos;
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uint16_t cmd;
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uint8_t mem[32];
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} Rtc;
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static Rtc rtc;
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void rtcTick() {
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int x;
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for (x=0; x<3; x++) {
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rtc.mem[x]++;
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if (rtc.mem[x]!=0) break;
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}
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for (int i=0; i<4; i++) rtc.mem[i+4]=rtc.mem[i]; //undocumented; mac needs it tho'.
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}
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extern void saveRtcMem(char *mem);
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int rtcCom(int en, int dat, int clk) {
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int ret=0;
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clk=clk?1:0;
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if (en) {
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rtc.pos=0;
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rtc.cmd=0;
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} else {
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if (clk!=rtc.lastClkVal && clk) {
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if (rtc.pos<8 || (rtc.pos<16 && ((rtc.cmd&0x8000)==0)) ) {
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//First 8 bits, or all 16 bits if write: accumulate data
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if (dat) rtc.cmd|=(1<<(15-rtc.pos));
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}
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// printf("RTC: clocktick %d, dataline %d, cmd %x\n", rtc.pos, dat, rtc.cmd);
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if (rtc.cmd&0x8000) { //read
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if (rtc.pos==8) {
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rtc.cmd|=rtc.mem[(rtc.cmd&0x7C00)>>10];
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// printf("RTC: Read cmd %x val %x\n", rtc.cmd>>8, (rtc.cmd&0xff));
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}
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ret=((rtc.cmd&(1<<(15-rtc.pos)))?1:0);
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} else if (rtc.pos==15) {
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// printf("RTC: Write cmd %x\n", rtc.cmd>>8);
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rtc.mem[(rtc.cmd&0x7C00)>>10]=rtc.cmd&0xff;
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saveRtcMem((char*)rtc.mem);
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}
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rtc.pos++;
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}
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}
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rtc.lastClkVal=clk;
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return ret;
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}
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void rtcInit(char *mem) {
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memcpy(rtc.mem, mem, 32);
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}
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