TLV5616C, TLV5616I

2.7 V TO 5.5 V LOW POWER 12-BIT DIGITAL-TO-ANALOG

CONVERTERS WITH POWER DOWN

SLAS152B – DECEMBER 1997 – REVISED MARCH 1999

16

POST OFFICE BOX 655303

APPLICATION INFORMATION

LJMP

start

; Execution starts at address 0 on power–up.

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

; Code in the timer0 interrupt vector

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

CSEG AT

0BH

LJMP

timer0isr ; Jump vector for timer 0 interrupt is 000Bh

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

; Define program variables

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

RSEG

VAR1

rolling_ptr: DS

1

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

; Interrupt service routine for timer 0 interrupts

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

RSEG

ISR

timer0isr:

PUSH

PSW

PUSH

ACC

CLR

T0

; set CSB low

CLR

T1

; set FS low

; The signal to be output on the dac is a sine function. One cycle of a sine wave is

; held in a table @ sinevals as 32 samples of msb, lsb pairs (64 bytes). The pointer,

; rolling_ptr, rolls round the table of samples incrementing by 2 bytes (1 sample) on

; each interrupt (at the end of this routine).

MOV

DPTR,#sinevals

; set DPTR to the start of the table of sine signal values

MOV

A,rolling_ptr

; ACC loaded with the pointer into the sine table

MOVC

A,@A+DPTR

; get msb from the table

ORL

A, #00H

; set control bits

MOV

SBUF,A

; send out msb of data word

MOV A,rolling_ptr ; move rolling pointer in to ACC

INC

A

; increment ACC holding the rolling pointer

MOVC

A,@A+DPTR

; which is the lsb of this sample, now in ACC

MSB_TX:

JNB

TI, MSB_TX

; wait for transmit to complete

CLR

TI

; clear for new transmit

MOV

SBUF,A

; and send out the lsb

LSB_TX:

JNB

TI, LSB_TX

; wait for lsb transmit to complete

SETB

T1

; set FS = 1

CLR

TI

; clear for new transmit

MOV

A,rolling_ptr

; load ACC with rolling pointer

INC

A

; increment the ACC twice, to get next sample

INC

A

ANL

A,#03FH

; wrap back round to 0 if >64

MOV

rolling_ptr,A

; move value held in ACC back to the rolling pointer

SETB

T0

; CSB high

POP

ACC

POP

PSW

RETI

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

; Set up stack

;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––