dtmf.s03

This contains a pdf file for DTMF

; The following code uses both timers in an 80c31 to generate
; DTMF tones, and signalling tones such as BUSY, RING-BACK, etc.
; This file also contains the connections for a very crude 2 bit
; per tone A\D converter wich uses 4 bits of P1 and a low pass filter.
; Compensation for twist isn't included but could be handled by
; playing with the hi and low tone dac values and the summing amp
; input resistors.
;
; If this code is used in any application I only request that
; credit be given to me: 
;	Bert Rinne
;	Advanced Logic Systems Inc.
;	13 Twin Meadows Dr.
;	Hudson N.H. 03051
;	(C) 1993
;
;	Note: This code was written for the Archemedes assembler
;	but modification to other's sould be easy since I've
;	avoided MACRO's to ease the change
;
;	Use in good health
;
;	*** Another method of tone generation is documented in the
;	'YUCK' Zilog Z8 microcontrollers book circa 1991 using the
;	Super8. It is a waveform synthesis model using a 8Khz sampled
;	data system with 1 timer and an 8 bit dac. If anyone should
;	adapt the technique to the '51/'31 family please post the
;	code on this BBS in return for the info.
;		
;					Bert Rinne 12/93
;
        ASEG	;this denotes absolute assembly addresses
; next 2 lines are for simulation using EMILY

;    org 0	;commented out for the 31 monitor used
;    jmp test

        org     0bh
        jb      INT_FLAGS.1,TICK0

        jmp     T0INT                   ;generate waveforms
TICK0:
        jmp     TICTOC0                 ;10mS ony timer

        org     001bh
        jmp     T1INT

INT_FLAGS       equ     020h    ;interrupt routine flags
SIGNAL_LOW      equ     021h    ;2 bytes for signal fLOW timer
SIGNAL_HIGH     equ     023h    ;2 bytes for signal fHIGH timer
fHIGH           equ     025h
fLOW            equ     026h
CNT_10mS        equ     027h

Reg0            equ     0


        org     03000h          ;temp address

;================================
; the following code loads the dialing array
; with the values needed for dtmf tone generation
; ENTER:        <ACC> = dtmf or signal tone number
;               ie. 0123456789 ABCD
;               or  * = 0eH  # = 0fH
;               dial tone = 080h
;               ring back = 081h
;               busy      = 082h
;	

; first parse 0-9, ABCD, *#, from signal group
LOAD_DTMF:
        clr     INT_FLAGS.1             ;flag dtmf timer mode
        anl     IE,#11110101b           ;timer ints. off
        anl     TCON,#10101111b         ;stop timers
        jbc     acc.7,SIGNAL            ;Go if signal

        mov     TMOD,#022h              ;T0 = T1 = 8 bit Auto-reload
        anl     a,#0fh                  ;strip any trash
        rl      a                       ;* 2
        rl      a                       ;* 4 total
        mov     b,a                     ;save a copy
        mov     dptr,#TONE_TBL          ;point at table
        movc    a,@a+dptr               ;get fLOW
        mov     TL1,a                   ;set T1 low
        mov     TH1,a                   ;set reload latch
        inc     dptr                    ;to next entry
        mov     a,b                     ;get index
        movc    a,@a+dptr               ;get fHIGH
        mov     TL0,a                   ;set T0 low
        mov     TH0,a                   ;and the latch
        inc     dptr                    ;bump to 10 mS count
        mov     a,b                     ;the index
        movc    a,@a+dptr               ;get count
        mov     CNT_10mS,a              ;put 10mS count in place
        setb    INT_FLAGS.0             ;flag ISR 0
        orl     IE,#00001010b           ;enable T0 and T1 intr's
        ret                             ;bye

;
; If we come here it's from the signal group
; so we use the 16 bit timer modes 
;
; see if it's dial tone
SIGNAL:
        mov     TMOD,#11H               ;set 16 bit timer modes
        jnz     not_dial_tone           ;go if not dial tone

; if here it's dial tone
        mov     dptr,#F440+2            ;440 Hz
        mov     TL0,DPL
        mov     TH0,DPH
        mov     SIGNAL_HIGH+1,DPL
        mov     SIGNAL_HIGH,DPH

        mov     dptr,#F350+2            ;350 Hz
        mov     TL1,DPL
        mov     TH1,DPH
        mov     SIGNAL_LOW+1,DPL
        mov     SIGNAL_LOW,DPH
        mov     CNT_10mS,#28            ;10 mS for count
        clr     INT_FLAGS.0             ;fag 16 bit timer ops
        orl     IE,#00001010b           ;enable T1 and T2 intr's
        ret

; not dial tone so see if it's ring-back
not_dial_tone:
        dec     a                       ;see if it's ring back
        jnz     not_ring_back           ;fork if not

        mov     dptr,#F480+2            ;adjust for intr latency
        mov     TL0,DPL
        mov     TH0,DPH
        mov     SIGNAL_HIGH+1,DPL
        mov     SIGNAL_HIGH,DPH

        mov     dptr,#F440+2            ;440 Hz
        mov     TL1,DPL
        mov     TH1,DPH
        mov     SIGNAL_LOW+1,DPL
        mov     SIGNAL_LOW,DPH
        mov     CNT_10mS,#36            ;count for 10 mS
        clr     INT_FLAGS.0             ;fag 16 bit timer ops
        orl     IE,#00001010b           ;enable T1 and T2 intr's
        ret

; not ring-back so assume it's busy
not_ring_back:
        
        mov     dptr,#F620+2            ;620 Hz
        mov     TL0,DPL
        mov     TH0,DPH
        mov     SIGNAL_HIGH+1,DPL
        mov     SIGNAL_HIGH,DPH

        mov     dptr,#F480+2          ;480 Hz
        mov     TL1,DPL
        mov     TH1,DPH
        mov     SIGNAL_LOW+1,DPL
        mov     SIGNAL_LOW,DPH
        mov     CNT_10mS,#39            ;count for 10 mS 
        clr     INT_FLAGS.0             ;fag 16 bit timer ops
        orl     IE,#00001010b           ;enable T1 and T2 intr's
        ret

;
;   HARDWARE CONFIGURATION                     ____/\/\/\___
;--------,                                     |           |
; 8031   |      47k                            +-----][----|
;   P1.0 |-----/\/\/\------,                   |           |
;        |      12k        +--/\/\/\--,        |    \      |
;   P1.1 |-----/\/\/\------'          |        |   |   \   |
;        |                            +---][---+---|-    \_|____||___ 
;        |      47k                   |            |     /      ||
;   P1.2 |-----/\/\/\------,          |         ,--|+  /
;        |      12k        |--/\/\/\--'         |  |/
;   P1.3 |-----/\/\/\------'                    | 
;--------'                                      +2.5V
; 
; the dac uses 3 bits per channel internal to the mpu and
; counts as follows 000 001 010 011 100 101 110 111
; using bit 2 as the sign and complementing bits 0 & 1 we
; get 000 001 010 011 111 110 101 100 and
; output 00 01 10 11 11 10 01 00
; The above was coupled to a 100mw amp and used to dial the phone
; via acoustical coupling (held phone near speaker) with no errors.
;
; Funky DAC courtesy of Don Lancaster's wonderful book - 
; The CMOS Cookbook, Howard Sams Inc.
;
;       DIALING TONES (dtmf)
;
;                       1209    1336    1477    1633
;
;               697       1       2       3       A
;
;               770       4       5       6       B
;
;               852       7       8       9       C
;
;               941       *       0       #       D 
;
;   Using the formula  f = -(((osc/12)/bits-per-cycle)/desired-freq.)
;
;   thus at 11.059 MHz clock and 8 bits per cycle:
;
;     desired        timer value     actual freq
;       697     =       -165            698.2
;       770     =       -150            768
;       852     =       -135            853.3
;       941     =       -122            944
;
;       1209    =       -95             1212.6
;       1336    =       -86             1339.5
;       1477    =       -78             1476.9
;       1633    =       -71             1622.5

F697    equ     LOW(-165)
F770    equ     LOW(-150)
F852    equ     LOW(-135)
F941    equ     LOW(-122)
;
F1209   equ     LOW(-95)
F1336   equ     LOW(-86)
F1477   equ     LOW(-78)
F1633   equ     LOW(-71)
;
;       Tone time on    >40 mS          Bell spec minimum so we
;       Tone time off   >40 mS          will use 100mS on/70 mS off
;
;       SIGNAL TONES
; NOTE *** the signal tone values are adjusted by LOAD_DTMF:
; to compensate for latency time while re-loading the timers. 
; The latency time is 2 us. and is critical for 
; valid signal tone frequencies.
;
;
;       Dial tone       350  440         steady tone            -13dBm
;       ring-back       440  480         2 sec on/ 4 sec off    -19dBm
;       busy            480  620        .5 sec on/.5 sec off    -24dBm
; NOTE: *******
;	Although the following are not implemented, they are valid
;	signal tones:
;
;	Reorder:	480  620	.25 sec on/.25 sec off	-24dBm
;
;	Partial dial tone
;			480		steady tone		-17dBm
;
;	Auto credit call prompting:
;			941  1477	940 mSEC		-10dBm/freq.
;	followed by	440  350	exponentially decaying from -10dBm
;					@ a time constant of 200mSec.
;
;	Reference:	Mitel Semiconductor Data book circa '86-'87.
;			"Credit must be given where due."
;
;	Pulse dialing can be accomplished very easily using the timers
;	and if you're reading this you can figure it out.
;
;     desired        timer value     actual freq
;       350             -329            350
;       440             -262            439.7
;       480             -240            480
;       620             -186            619

F350    equ     -329     
F440    equ     -262
F480    equ     -240
F620    equ     -186

TONE_TBL:
; 0
        db      F941                    ;fLOW  = 941  
        db      F1336                   ;fHIGH = 1336 
        db      76                      ;76 * fLOW intrs = 10mS
        db      0
; 1
        db      F697                    ;fLOW  = 697  
        db      F1209                   ;fHIGH = 1209 
        db      56                      ;56 * fLOW intrs = 10 mS
        db      0
; 2
        db      F697                    ;fLOW  = 697  
        db      F1336                   ;fHIGH = 1336 
        db      56
        db      0
; 3
        db      F697                    ;fLOW  = 697  
        db      F1477                   ;fHIGH = 1477 
        db      56
        db      0
; 4
        db      F770                    ;fLOW  = 770  
        db      F1209                   ;fHIGH = 1209 
        db      62
        db      0
; 5
        db      F770                    ;fLOW  = 770  
        db      F1336                   ;fHIGH = 1336 
        db      62
        db      0