Documentation

Original schematics, firmware source code, hardware photos, and technical reference for the 1991 HACKTIC Demon Dialer.

Schematic

The original schematic (v1.00) shows the complete circuit: MC68HC05C8 CPU, 4×3 keypad matrix on PORTB/PORTD, 7-bit R-2R DAC ladder on PORTC for audio output, and RS-232 serial interface via the on-chip SCI.

Schematic v1.00 — Original HACKTIC design

Hardware

Original Demon Dialer v1.10

The original HACKTIC-produced unit with MC68HC05C8 one-time-programmable CPU. The PCB measures approximately 55×35mm and connects to a standard 4×3 keypad module.

CPU side — MC68HC05C8 + crystal

Keypad side — 4×3 matrix

Don Froula's Build

Don Froula recreated the Demon Dialer using the UV-erasable MC68HC705C8S variant, allowing firmware development and debugging. His build progressed from breadboard prototype to finished perfboard unit.

Breadboard prototype

Perfboard build

Completed unit

Inside the enclosure

Wiring detail

Component layout

Programming Setup

Programming the MC68HC705C8S required a dedicated programmer board and DOS/Windows 95 software to burn the firmware onto the UV-erasable chip.

UV-erasable MC68HC705C8S — windowed ceramic package

M68HC05 Programmer Board

Complete programming setup

Win95 programmer software

Original Packaging

Original packaging — front

Original packaging — back

Firmware Source Code

The complete firmware is 3,991 lines of Motorola 68HC05 assembly (demon131.asm, v1.31). Below are key excerpts showing the tone generation engine and frequency tables.

Memory Map & Variables

                demon131.asm — RAM Variables (ORG $0030)
                Lines 64–98
            
 ORG $0030

                TONE1CT RMB 2
                ; Tone 1 counter value
                TONE1ST RMB 2
                ; Tone 1 step value
                TONE2CT RMB 2
                ; Tone 2 counter value
                TONE2ST RMB 2
                ; Tone 2 step value
                TONEOUT RMB 1
                ; Current output sample
                TONE1 RMB 3 ; JMP instruction for tone 1 handler
                TONE2 RMB 3 ; JMP instruction for tone 2 handler
                TONE3 RMB 3 ; JMP instruction for tone 3 handler
                TICKER RMB 2 ; 8.192 kHz ticker (tone duration)

                KEYBUF RMB 4 ; 4-byte keyboard buffer
                KEYS RMB 1 ; # of keys in keyboard buffer
                MODE RMB 1 ; Current operating mode (piom mmmm)
            

Frequency Table

                demon131.asm — FREQTBL
                Lines 221–277
            
 ORG $0148

                FREQTBL RMB 24
                ; 12 user-definable frequencies

                FDB 5600 ; 12 — 700 Hz
                    ─┐
                FDB 7200 ; 13 — 900 Hz
                    │
                FDB 8800 ; 14 — 1100 Hz
                    ├─ MF
                FDB 10400 ; 15 — 1300
                    Hz │
                FDB 12000 ; 16 — 1500
                    Hz │
                FDB 13600 ; 17 — 1700
                    Hz ─┘

                FDB 5558 ; 18 — 694.8
                    Hz ─┐
                FDB 6161 ; 19 — 770.1
                    Hz │
                FDB 6819 ; 20 — 852.4
                    Hz ├─ DTMF Rows
                FDB 7520 ; 21 — 940.0
                    Hz ─┘
                FDB 9648 ; 22 — 1206.0
                    Hz ─┐
                FDB 10654 ; 23 — 1331.7
                    Hz ├─ DTMF Cols
                FDB 11892 ; 24 — 1486.5
                    Hz │
                FDB 13112 ; 25 — 1639.0
                    Hz ─┘

                FDB 11040 ; 26 — 1380
                    Hz ─┐
                FDB 12000 ; 27 — 1500
                    Hz ├─ R2 Forward
                FDB 12960 ; 28 — 1620
                    Hz │
                FDB 13920 ; 29 — 1740
                    Hz │
                FDB 14880 ; 30 — 1860
                    Hz │
                FDB 15840 ; 31 — 1980
                    Hz ─┘

                FDB 17600 ; 40 — 2200
                    Hz Red Box
                FDB 19200 ; 53 — 2400
                    Hz Supervisory
                FDB 20800 ; 55 — 2600
                    Hz Blue Box
            

DTMF Tone Data Table

                demon131.asm — ROMMDS (DTMF Mode)
                Lines 3340–3370
            
; DTMF key mapping: format byte, dB level, freq1 index,
                    freq2 index
                ; Format byte bits: play-while-pressed, timing, tone count

                DTMF FCB %01011010,$66,18,22 ; 1 → 694.8 + 1206.0 Hz
                FCB %10011011
                FCB %01011010,$66,18,23 ; 2 → 694.8 + 1331.7 Hz
                FCB %10011011
                FCB %01011010,$66,18,24 ; 3 → 694.8 + 1486.5 Hz
                FCB %10011011
                FCB %01011010,$66,19,22 ; 4 → 770.1 + 1206.0 Hz
                FCB %10011011
                FCB %01011010,$66,19,23 ; 5 → 770.1 + 1331.7 Hz
                FCB %10011011
                ; ... continues for all 12 keys + shifted keys
            

Tone Generation Engine

                demon131.asm — Timer Interrupt (8192 Hz)
                Lines 3050–3090
            
; The timer interrupt fires at 8192 Hz.
                ; Each tick: adds step to counter, uses high byte as sine table index.
                ; Two independent tone generators are summed and output to PORTC.

                TON1_A LDA TONE1CT ; Load 16-bit counter low byte
                ADD TONE1ST+1 ; Add
                    step low byte
                STA TONE1CT ; Store
                    counter low
                LDA TONE1CT+1 ; High
                    byte
                ADC TONE1ST ; Add step
                    high (with carry)
                STA TONE1CT+1 ; Store
                    counter high
                TAX ; X = counter high byte = sine index
                LDA SINTBL,X ; Look up
                    in 256-entry sine table
                ADD #64 ; Add DC
                    offset (center at $40)
                STA TONEOUT ; → 7-bit
                    DAC value on PORTC
            

Tone Reference

DTMF Frequencies

	1209 Hz	1336 Hz	1477 Hz	1633 Hz
697 Hz	1	2	3	A
770 Hz	4	5	6	B
852 Hz	7	8	9	C
941 Hz	*	0	#	D

MF (Blue Box) Frequencies

Digit	Frequency 1	Frequency 2
1	700 Hz	900 Hz
2	700 Hz	1100 Hz
3	900 Hz	1100 Hz
4	700 Hz	1300 Hz
5	900 Hz	1300 Hz
6	1100 Hz	1300 Hz
7	700 Hz	1500 Hz
8	900 Hz	1500 Hz
9	1100 Hz	1500 Hz
0	1300 Hz	1500 Hz
KP	1100 Hz	1700 Hz
KP2	1300 Hz	1700 Hz
ST	1500 Hz	1700 Hz
2600	2600 Hz single tone

Red Box Coin Tones

Coin	ACTS	Pattern
5¢ (Nickel)	1700 + 2200 Hz	1 × 66ms burst
10¢ (Dime)	1700 + 2200 Hz	2 × 66ms bursts, 66ms gap
25¢ (Quarter)	1700 + 2200 Hz	5 × 33ms bursts, 33ms gap

External Resources

Hacktic Magazine #14/15 (1991) — hacktic.nl/magazine/1448.htm

Project MF — Originally created by Phiber Optik (Mark Abene) as a living simulation of a blueboxable phone line: projectmf.com (archived)