add toggle detection tape monitor

demos/tapemon/m.bat

@@ -1,4 +1,8 @@
 @call ..\..\tools\build tapemon
 @call node ..\..\tools\prg2bin -i out\tapemon_apple1.prg -o out\tapemon.0280.bin
 
+@call ..\..\tools\build tapetoggle
+@call node ..\..\tools\prg2woz -i out\tapetoggle_apple1.prg -o out\tapetoggle.0280.woz
+
+
 

demos/tapemon/tapetoggle.c

@@ -0,0 +1,22 @@
+#include <utils.h>
+#include <apple1.h>
+
+byte *const LASTSTATE  = 0x29;             // Last input state
+byte *const TAPEIN     = 0xC081;           // Tape input
+byte *const DSP        = 0xD012;           // display data port
+
+void main()
+{
+   asm {
+simple_monitor:   lda TAPEIN               // read tape input
+                  cmp LASTSTATE            // compare to previous state
+                  beq no_toggle            // if same just skip
+                  sta LASTSTATE            // else save new state
+                  ldx #35                  // set "toggle detected" flag in X, 35 is also the char to print
+no_toggle:        bit DSP                  // check if display is ready to accept a character
+                  bmi simple_monitor       // if not, just keep reading tape
+                  stx DSP                  // else display the "toggle detected" flag character
+                  ldx #45                  // resets the "toggle detected" flag to the "-" sign, sets also Z=0 flag
+                  bne simple_monitor       // cheap jump because Z is also 0
+   }
+}