;Example 2 - 23. Creation of a Sine Wave ASM Listing Based on Oscillator Using TMS320C62x
.def init
int .equ 4
half .equ 2
.data
a_half .short 32768*1975/2000
y1 .short 32768*1409/10000
y2 .short 0
.bss output,40*half,half
.bss buffer,2*half,2*half
.text
init:
MVK .S1 a_half, A0
MVKH .S1 a_half, A0
LDH .D1 *A0, A2 ; load coeff A_HALF
MVK .S1 0x0001, A0 ; setup circular buf AMR=0001_0001h
MVKLH .S1 0x0001, A0 ; setup circular buf AMR=0001_0001h
MVC .S2X A0, AMR ; blk size is 4 bytes, pointer is A4
MVK .S1 output, A3 ; memory for store sine wave
MVKH .S1 output, A3
MVK .S1 0, A0
STH .D1 A0, *A3++ ; output y(0)=0 to IOPORT
MVK .S1 buffer, A4
MVKH .S1 buffer, A4
MVK .S1 y1, A0
MVKH .S1 y1, A0
LDH .D1 *A0++, A1 ; load y1
NOP 4
STH .D1 A1, *A4++ ; y(n–1)=y1, point to y(n–2)
STH .D1 A1, *A3++ ; output y(1)=y1 to IOPORT
LDH .D1 *A0, A1 ; load y2
NOP 4
STH .D1 A1, *A4++ ; y(n–2)=y2, point to y(n–1)
main: MVK .S1 40, A1 ; calculate 40 samples
loop: LDH .D1 *A4++, B1 ; ld y(n–1) to B1, point to y(n–2)
LDH .D1 *A4, B2 ; ld y(n–2) to B2, point to y(n–2)
NOP 3 ; SMPY .M1X A2, B1, A0 ; A_HALF*y(n–1)
SUB .L1 A1, 1, A1
[A1] B .S1 loop
SHR .S1 A0, 16, A0 ; SADD .L1 A0, A0, A0 ; A_HALF*y(n–1)*2
SSUB .L2X A0, B2, B0 ; A_HALF*y(n–1)*2–y(n–2)
STH .D1 B0, *A4 ; st y(n) to y(n–2) as y(n–1)
STH .D1 B0, *A3++ ; st y(n) to Sine wave IOPORT
end: B .S1 $
NOP 5
