diff --git a/demos/tapemon/README.md b/demos/tapemon/README.md
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+# TAPEMON
+
+Tapemon is a Apple-I tool that helps finding the optimal playback volume to
+the ACI audio cassette interface.
+
+## How to use it
+
+- Load `tapemon.0280.bin` on the Apple-1 and execute it with `280R`.
+
+- Connect your playback device (PC, Smartphone, iPod etc) to the ACI
+
+- Play the file `frames.wav` contained in `frame/frames.wav.zip` archive. The file
+will send a continous stream of small data packets that are catched by the program
+running on the Apple-1. Each packet is 64 bytes long.
+
+For each received packet a character will be displayed:
+
+- `*` indicates a good packet
+- `.` indicates packet not received
+- an hex digit 0-F indicates the packet is partially corrupt
+
+Adjust the volume level so that you have a lot of `*`.
+
+
+
+
+
+
+
+
diff --git a/demos/tapemon/frame/frames.wav.zip b/demos/tapemon/frame/frames.wav.zip
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index 0000000..704fe2b
Binary files /dev/null and b/demos/tapemon/frame/frames.wav.zip differ
diff --git a/demos/tapemon/frame/mkframes.js b/demos/tapemon/frame/mkframes.js
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+const fs = require("fs");
+
+const FRAMELEN = 64;
+
+let data_block = [];
+for(let t=0;t<FRAMELEN;t++) data_block.push(t);
+
+let frame = [
+   0xff, 0xff, 0xff, 0xff, 0xfe,       // header plus start bit
+   ...data_block,                      // the actual data block
+   0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55, // filler
+]
+
+let frames = [];
+
+for(let t=0;t<1000;t++) {
+   frames = [...frames, ...frame];
+}
+
+let data = new Uint8Array(frames);
+
+fs.writeFileSync("frames.bin", data);
+
+
diff --git a/demos/tapemon/frame/mw.bat b/demos/tapemon/frame/mw.bat
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+++ b/demos/tapemon/frame/mw.bat
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+call node mkframes
+call node ..\..\..\..\apple1-wav\prg2wav.js -i frames.bin -o frames -b 00
\ No newline at end of file
diff --git a/demos/tapemon/m.bat b/demos/tapemon/m.bat
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+++ b/demos/tapemon/m.bat
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+@call ..\..\tools\build tapemon
+
diff --git a/demos/tapemon/tapemon.c b/demos/tapemon/tapemon.c
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+++ b/demos/tapemon/tapemon.c
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+#include <utils.h>
+#include <apple1.h>
+
+const byte *HEX1L      = 0x24;             // End address of dump block
+const byte *HEX1H      = 0x25;             //
+const byte *HEX2L      = 0x26;             // Begin address of dump block
+const byte *HEX2H      = 0x27;             //
+const byte *LASTSTATE  = 0x29;             // Last input state
+const byte *NUMPULSES  = 0x30;             // Number of long pulses to sync at the header
+const byte *TAPEIN     = 0xC081;           // Tape input
+
+#define FRAMELEN 64
+
+const byte *RX_BUFFER = 0x200;
+const byte *RX_BUFFER_END = (0x200+FRAMELEN-1);
+
+void read_frame()
+{
+   asm {
+                // set READ buffer pointers to $0200-$021F (32 characters)
+                lda     #<RX_BUFFER_END
+                sta     HEX1L
+                lda     #>RX_BUFFER_END
+                lda     HEX1H
+
+                lda     #<RX_BUFFER
+                sta     HEX2L
+                lda     #>RX_BUFFER
+                lda     HEX2H
+
+                // synchronizes with the short header
+
+syncstart:      lda     #24           // 24 cycles (3 bytes of $ff)
+                sta     NUMPULSES     // count 24 cycles pulses
+                jsr     fullcycle     // skip the first full cycle (when looping)
+nextsync:       ldy     #58           // full cycle duration
+                jsr     fullcycle     // read a full cycle
+                bcc     syncstart     // if short cycle found (c=0), redo from start
+                dec     NUMPULSES     // else long cycle found, decrease count
+                bne     nextsync      // if not 24 cycles, get next cycle
+
+                // else read bit start and 32 bytes of data normally
+                // the following routine was copied directly from the ACI ROM
+
+notstart:       ldy     #31           // try to detect the much shorter start bit
+                jsr     cmplevel      //
+                bcs     notstart      // start bit not detected yet!
+                jsr     cmplevel      // wait for 2nd phase of start bit
+                ldy     #58           //  set threshold value in middle
+rdbyte:         ldx     #8            //  receiver 8 bits
+rdbit:          pha
+                jsr     fullcycle     //  detect a full cycle
+                pla
+                rol                   //  roll new bit into result
+                ldy     #57           //  set threshold value in middle
+                dex                   //  decrement bit counter
+                bne     rdbit         //  read next bit!
+                sta     ($26,x)       //  save new byte   *** same as "STA (HEX2L,X)" see KickC bug #756 https://gitlab.com/camelot/kickc/-/issues/756
+                jsr     incaddr       //  increment address
+                ldy     #53           //  compensate threshold with workload
+                bcc     rdbyte        //  do next byte if not done yet!
+                bcs     restidx       //  always taken! restore parse index
+fullcycle:      jsr     cmplevel      //  wait for two level changes
+cmplevel:       dey                   //  decrement time counter
+                lda     TAPEIN        //  get tape in data
+                cmp     LASTSTATE     //  same as before?
+                beq     cmplevel      //  yes!
+                sta     LASTSTATE     //  save new data
+                cpy     #128          //  compare threshold
+                rts
+                // [...]
+incaddr:        lda     HEX2L         //  compare current address with
+                cmp     HEX1L         //   end address
+                lda     HEX2H
+                sbc     HEX1H
+                inc     HEX2L         //  and increment current address
+                bne     nocarry       //  no carry to msb!
+                inc     HEX2H
+nocarry:        rts
+
+                // end of read routine "restidx" is the exit point
+
+restidx:        rts
+
+   }
+}
+
+byte data_block[FRAMELEN];
+byte *vmeter = "0123456789ABCDEF";
+
+void main() {
+
+   // fill the data block with the known values
+   for(byte t=0;t<FRAMELEN;t++) data_block[t] = t;
+
+   woz_puts("\r\rTAPE MONITOR\r\r");
+
+   // tape monitor loop
+   for(;;) {
+      read_frame();  // attempt reading 1 data block
+
+      // compare received data block with known data
+      byte i;
+      for(i=0;i<FRAMELEN;i++) {
+         if(RX_BUFFER[i] != data_block[i]) break;
+      }
+
+      // display result
+           if(i==0)        woz_putc('.');
+      else if(i==FRAMELEN) woz_putc('*');
+      else {
+         #if FRAMELEN == 32
+         woz_putc(vmeter[i>>1]);
+         #endif
+         #if FRAMELEN == 64
+         woz_putc(vmeter[i>>2]);
+         #endif
+      }
+
+      // exit with "X"
+      if(apple1_readkey()=='X') break;
+   }
+}
+