add viaclock demo

demos/viatimer/m.bat

@@ -1,2 +1,3 @@
-@call ..\..\tools\build viatimer
+rem @call ..\..\tools\build viatimer
+@call ..\..\tools\build viaclock
 

demos/viatimer/viaclock.c

@@ -0,0 +1,99 @@
+#define APPLE1_USE_WOZ_MONITOR 1
+
+#define INPUT_LINE_PROMPT_CHAR '?'
+
+#include <string.h>
+
+#include <utils.h>
+#include <apple1.h>
+#include <via.h>
+#include <interrupt.h>
+#include <stdlib.h>
+#include <division.h>
+
+#include "..\..\lib\c64font.h"
+
+const word ONE_TICK = 16666;  // timer constant for 1/60 second
+
+void enable_timer_interrupt() {
+
+   // install the interrupt handler
+   install_interrupt((word) &time_interrupt_handler);
+
+   *VIA_IER  = 0b11000000;       // enable T1 interrupts
+   *VIA_ACR  = 0b01000000;       // T1 continous, PB7 disabled
+   *VIA_T1CL = BYTE0(ONE_TICK);  // programs the counter to 1/60
+   *VIA_T1CH = BYTE1(ONE_TICK);  // and starts counting
+}
+
+void disable_timer_interrupt() {
+   *VIA_IER  = 0b01000000;   // disable T1 interrupts
+   *VIA_ACR  = 0;            // stop T1 (makes it one-shot)
+}
+
+byte last_min = 0xFF;
+
+void print_digit_scanline(byte c, byte y) {
+   word index = ((word) c-32) * 8 + (word) y;
+   byte *ptr = FONT + index;
+
+   byte mask = 128;
+   for(byte t=0;t<8;t++) {
+      if(*ptr & mask) woz_putc('@');
+      else            woz_putc(' ');
+      mask = mask >> 1;
+   }
+}
+
+void print_clock() {
+   byte c1,c2,c3,c4;
+
+   if(last_min != _minutes) {
+      last_min = _minutes;
+
+      c1 = divr8u(_hours, 10, 0); c2 = rem8u;
+      c3 = divr8u(_minutes, 10, 0); c4 = rem8u;
+
+      woz_puts("\r\r\r\r\r\r\r\r");
+      for(byte t=0;t<8;t++) {
+         print_digit_scanline(c1+'0',t);
+         print_digit_scanline(c2+'0',t);
+         print_digit_scanline(   ':',t);
+         print_digit_scanline(c3+'0',t);
+         print_digit_scanline(c4+'0',t);
+      }
+      woz_puts("\r\r\r\r\r\r\r\r");
+   }
+}
+
+void bye() {
+   disable_timer_interrupt();
+   woz_puts("BYE!\r");
+   woz_mon();
+}
+
+byte  *const KEYBUF = (byte  *) 0x0200;   // use the same keyboard buffer as in WOZ monitor
+
+void main() {
+   enable_timer_interrupt();
+
+   woz_puts("\r\r*** APPLE1 CLOCK ***\r\r");
+
+   woz_puts("\r\rREQUIRES A VIA 6522 AT $A000\r\r");
+
+   woz_puts("\rWHAT TIME IS IT (HOURS  ) "); apple1_input_line_prompt(KEYBUF, 2);
+   _hours = (byte) atoi(KEYBUF);
+   woz_puts("\rWHAT TIME IS IT (MINUTES) "); apple1_input_line_prompt(KEYBUF, 2);
+   _minutes = (byte) atoi(KEYBUF);
+
+   woz_putc('\r');
+
+   while(1) {
+      byte k = apple1_readkey();
+      if(k=='X') break;
+      print_clock();
+   }
+
+   bye();
+}
+