TLV5604

2.7-V TO 5.5-V 10-BIT 3-

µS QUADRUPLE DIGITAL-TO-ANALOG CONVERTERS

WITH POWER DOWN

SLAS176A – DECEMBER 1997 – REVISED SEPTEMBER 1998

15

POST OFFICE BOX 655303

APPLICATION INFORMATION

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

;

; Processor:

TMS320C203 runnning at 40 MHz;

; Description:

;

; This program generates a differential in-phase (sine) on (OUTA–OUTB) and it’s

; quadrature (cosine) as a differential signal on (OUTC–OUTD).

;

; The DAC codes for the signal samples are stored as a table of 64 12–bit values,

; describing 2 periods of a sine function. A rolling pointer is used to address the

; table location in the first period of

this waveform, from which the DAC A samples are

; read. The samples for the other 3 DACs are read at an offset to this rolling pointer:

; DAC

Function

Offset from rolling pointer;

;

A

sine

0

;

B

inverse sine

16

;

C

cosine

8

;

D

inverse cosine

24

;

; The on-chip timer is used to generate interrupts at a fixed rate. The interrupt

; service routine first pulses LDAC low to update all DACs simultaneously with the

; values which were written to them in the previous interrupt. Then all 4 DAC values are

; fetched and written out through the synchronous serial interface. Finally, the

; rolling pointer is incremented to address the next sample, ready for the next

; interrupt.

;

;

© 1998, Texas Instruments Incorporated

.include ”regs.asm”

; ––––––––––––––jump vectors––––––––––––––––––––––––––––––––––––––––––––––––––––––

.ps

0h

b

start

b

int1

b

int23

b

timer_isr

temp

.equ

0060h

r_ptr

.equ

0061

iosr_stat

.equ

0062h

DACa_ptr

.equ

0063h

DACb_ptr

.equ

0064h

DACc_ptr

.equ

0065h

DACd_ptr

.equ

0066h

; DAC control bits to be OR’ed onto data

; all fast mode

DACa_control

.equ

01000h

DACb_control

.equ

05000h

DACc_control

.equ

09000h

DACd_control

.equ

0d000h

.ds

02000h

sinevals

.word

00800h

.word

0097Ch

.word

00AE9h

.word

00C3Ah

.word

00D61h

.word

00E53h

.word

00F07h

.word

00F76h

.word

00F9Ch

.word

00F76h

.word

00F07h

.word

00E53h

.word

00D61h

.word

00C3Ah