OSCCON = $60 							'Set up internal oscillator

CS var portb.4 							'Enable or disable MT8888 tied to ground
RD var portb.5 							'Read Microprocessor input
WR var portb.6 							'Write Microprocessor input
RS var portb.7 							'Register Select

TRISB = %00000000						'Set portb to output

Init var byte 						
Control var byte
Dtmf var byte
Status var byte
w var byte
X var byte
y var byte
z var byte

data @1,%11000000,%10100000,%10101000,%10100000,%10101101,%10100000,%00001000,%00001110,%00000001,%00001110,%00000011,%00001110,%00000110 'Data starting at position #1

Gosub Initialization
gosub SetupControlRegister
gosub WriteTransmitRegister

Initialization:
		Gosub ReadStatusRegister
		for w = 2 to 4
		read w, Init 				  'Read data statement starting at location #2 and put in Init
		Init = Init & $0F			  'Mask off upper 4 bits with Logical AND
		portb = Init | %11100000   		  'Set upper 3 bits with Logical OR and send to portb
		pause 10 				  'Wait 1 millisecond (may not be needed)
       		low WR   				  'Take portb pin 6 low
       		pause 10 				  'Wait 1 millisecond (may not be needed)
      		high WR                        		  'take portb pin 6 high
      		pause 10
		Next w
		
Return

ReadstatusRegister:
		
		read 1, Status 				 'Read data statement starting at location #1 and put in Status   
		Status = Status & $0F			 'Mask off upper 4 bits with Logical AND
		portb = Status | %11100000 	 	 'Set upper 3 bits with Logical OR and send to portb
		pause 10 				 'Wait 1 millisecond (may not be needed)
       		low RD   			         'Take portb pin 5 low
       		pause 10 				 'Wait 1 millisecond (may not be needed)
      		high RD   				 'take portb pin 5 high
      		pause 10
Return


SetupControlRegister:
		
		for x = 5 to 6
		read x, Control 			 'Read data statement starting at location #6 and put in Control
		Control = Control & $0F		 	 'Mask off upper 4 bits with Logical AND
		portb = Control | %11100000  		 'Set upper 3 bits with Logical OR and send to portb
		pause 10 				 'Wait 1 millisecond (may not be needed)
       		low WR   				 'Take portb pin 6 low
       		pause 10 				 'Wait 1 millisecond (may not be needed)
      		high WR   				 'take portb pin 6 high
      		pause 10
		Next X
Return


WriteTransmitRegister:
		
		for y = 7 to 13               
		read y, Dtmf 				 'Read data statement starting at location #9 and put in Dtmf
		Dtmf = Dtmf & $0F			 'Mask off upper 4 bits with Logical AND
		portb = Dtmf | %11100000 	         'Set upper 3 bits with Logical OR and send to portb
		pause 10 				 'Wait 1 millisecond (may not be needed)
       		high RD   				 'Take portb pin 5 high
       		pause 10 				 'Wait 1 millisecond (may not be needed)
      		low RD     				 'take portb pin 5 low
      		pause 10
		Next y

Return


End

' Listing 1. Stamp-Based Autodialer
' Program: DIAL.SRC (Sends a string of DTMF tones via the 8880)
' This program demonstrates how to use the CM8880 as a DTMF tone
' generator. All that's required is to initialize the 8880 properly,
' then write the number of the desired DTMF tone to the 8880's
' 4-bit bus.
' The symbols below are the pin numbers to which the 8880's
' control inputs are connected, and one variable used to read
' digits out of a lookup table.
SYMBOL RS_p = 4 ' Register-select pin (0=data).
SYMBOL RW_p = 5 ' Read/Write pin (0=write).
SYMBOL CS_p = 6 ' Chip-select pin (0=active).
SYMBOL digit = b2 ' Index of digits to dial.
' This code initializes the 8880 for dialing by writing to its
' internal control registers CRA and CRB. The write occurs when
' CS (pin 6) is taken low, then returned high. See the accompanying
' article for an explanation of the 8880's registers.
let pins = 255 ' All pins high to deselect 8880.
let dirs = 255 ' Set up to write to 8880 (all outputs).
let pins = %00011011 ' Set up register A, next write to register B.
high CS_p
let pins = %00010000 ' Clear register B; ready to send DTMF.
high CS_p
Stamp Applications no. 7, September 1995
7
' This for/next loop dials the seven digits of my fax number. For
' simplicity, it writes the digit to be dialed directly to the output
' pins. Since valid digits are between 0 and 15, this also takes RS,
' RW, and CS low--perfect for writing data to the 8880. To complete
' the write, the CS line is returned high. The initialization above
' sets the 8880 for tone bursts of 200 ms duration, so we pause
' 250 ms between digits. Note: in the DTMF code as used by the phone
' system, zero is represented by ten (1010 binary) not 0. That's why
' the phone number 459-0623 is coded 4,5,9,10,6,2,3.
for digit = 0 to 6
lookup digit,(4,5,9,10,6,2,3),pins ' Write current digit to pins.
high CS_p ' Done with write.
pause 250 ' Wait to dial next digit.
next digit
end
' Listing 2.