Texas Instruments TMS 32C5x DSP

TMS320C5x User Manual

Instruction Fetch/Decode Section

TMS320C5x User Manual

ACC

T

P

Address Registers

RAM

TMS320C5x Data Processing Section

Key DSP Instructions MAC pma,dma – multiply/accumulate

ACC + P -> ACCpma x dma -> P(repeatable with pma+1)

MACD pma,dma -multiply/accumulate/delayACC + P -> ACCpma x dma -> Pdma -> dma+1 (move data for delay)(repeatable with pma+1)

ACC = AccumulatorP = Product Registerpma = prog. mem’y addressdma = data mem’y address

Other key operations Operand addressing Direct: ADD pma/dma Immediate: ADD #100 Indirect: ADD * Address in auxiliary register: AR0-AR7 ARP (Auxiliary Register Pointer) selects one of AR0-AR7 *+ increments address after fetch/ *- decrements address after fetch

T register: temporary multiplicand for 16x16 multiplier MPY instruction provides the multiplier LT dma/ind : mem -> TREG0 LTA dma/ind : load T, ACC=ACC+P LTD dma/ind : load T, ACC=ACC+P,move data LTP dma/ind : load T, P->ACC

Low-Pass Filter

IN Xn,PA0 ;read x(n)

ZAP ;A=P=0

MAC B,Yn

MAC C,Xn ;C=1-B

APAC ;A=A+P

SACH Yn ;save LSB

OUT Yn,PA1 ;out y(n)

)()1()1()()()1()()(

1)1()1(

)()()(

1

1

nxbnbynyzXbzYbzzY

bzb

bzzb

zXzYzH

−+−=−+=

−−

=−−

==

−

−

z-1 = “time delay”

Finite Impulse Response (FIR) Filter

LARP AR3 ;AR3 active pointerLAR AR3,#X0 ;point to X(n)ZAP ;A=P=0MAC C0,*- ;c0*x(n)MAC C1,*- ;+c1*x(n-1)MAC C2,*- ;+c2*x(n-2)APAC ;final A=A+PSACH Y ;save LSB

)2()1()()()()()(

210

21

102

−+−+=

++== −−

nxcnxcnxcny

zczcczXzYzH

Prog. Mem Data Mem.C0 X(n)C1 X(n-1)C2 X(n-2)

PID Controller

IN E0,PA0 ;new error e(n)LARP AR3 ;AR3 active pointerLAR AR3,#X0 ;point to e(n-2)ZAP ;A=P=0MAC c2,*- ;c2*e(n-2)MACD c1,*- ;+c1*e(n-1), move eMACD c0,* ;+c0*e(n), move eAPAC ;final A=A+PSACH An ;save LSBOUT An,PA1

)2()1()()1()( 210 −+−++−= necnecnecnana

Prog. Mem Data Mem.C0 e(n)C1 e(n-1)C2 e(n-2)

a(n)=control actione(n) = nth errorc0,c1,c2 constants

Basic sum of products

LARP AR3 ;AR3 active pointer

LAR AR3,#X0 ;point to X0

ZAP ;A=P=0

RPT #N ;repeat next instr. N times

MAC C0,*+ ;sum of products

APAC ;final A=A+P

SACH Y ;save LSB

∑=

=N

kk kxcY

0)(

Prog. Mem Data Mem.C0 X(0)C1 X(1)C2 X(2)….CN X(N)

Both pma and dma autoincrement for each MAC

Constants

Basic sum of products (correlation)

CNFP ;Config B0 as prog memoryLARP AR3 ;AR3 active pointerLAR AR3,#Y ;point to y(0)ZAP ;A=P=0RPT #N MAC X0,*+ ;sum of productsAPAC ;final A=A+PSACH Y ;save LSBCNFD ;B0 back to data memory

∑=

=N

kkykxY

0)()(

B0 RAM B1 RAMx(0) y(0)x(1) y(1)….x(N) y(N)

Temporarily program memory

FIR filter

Computers as Components 4e © 2016 Marilyn Wolf

(Programming Example 5.3)

int fir(int xnew) { /* given a new sample value, update the queue and compute the filter output */ int i; int result; /* holds the filter output */ circ_update(xnew); /* put the new value in */ for (i=0, result=0; i<CMAX; i++)

result += b[i] * circ_get(i); return result;}

Signal processing and circular buffer

Commonly used in signal processing: new data constantly arrives; each datum has a limited lifetime.

Use a circular buffer to hold the data stream.

d1 d2 d3 d4 d5 d6 d7

time t time t+1

Computers as Components 4e © 2016 Marilyn Wolf

Circular buffer

x1 x2 x3 x4 x5 x6

t1 t2 t3Data stream

x1 x2 x3 x4

Circular buffer

x5 x6 x7

Computers as Components 4e © 2016 Marilyn Wolf

Circular buffers

Indexes locate currently used data, current input data:

d1

d2

d3

d4

time t1

use

input d5

d2

d3

d4

time t1+1

useinput

Computers as Components 4e © 2016 Marilyn Wolf

Circular buffer in C#define CMAX 6 /* filter order */ int circ[CMAX]; /* circular buffer */ int pos; /* position of current sample */

void circ_update(int xnew) { /* compute the new head value with wraparound; the pos pointer moves from 0 to CMAX-1 */ pos = ((pos == CMAX-1) ? 0 : (pos+1)); /* insert the new value at the new head */ circ[pos] = xnew; }

void circ_init() { int i; for (i=0; i<CMAX; i++) /* set values to 0 */ circ[i] = 0; pos=CMAX-1; /* start at tail so first element will be at 0 */ }

int circ_get(int i) { int ii; /* compute the buffer position */ ii = (pos - i) % CMAX; return circ[ii]; /* return the value */ }

Computers as Components 4e © 2016 Marilyn Wolf

IIR direct form type II filter

Computers as Components 4e © 2016 Marilyn Wolf

int iir2(int xnew) { int i, aside, bside, result; for (i=0, aside=0; i<ZMAX; i++)

aside += -a[i+1] * circ_get(i); for (i=0, bside=0; i<ZMAX; i++)

bside += b[i+1] * circ_get(i); result = b[0] * (xnew + aside) + bside; circ_update(xnew); /* put the new value in */ return result; }

(Programming Example 5.4)

Other key operations Operand addressing Direct: ADD pma/dma Immediate: ADD #100 Indirect: ADD * Address in auxiliary register: AR0-AR7 ARP (Auxiliary Register Pointer) selects one of AR0-AR7 *+ increments address after fetch/ *- decrements address after fetch

T register: temporary multiplicand for 16x16 multiplier MPY instruction provides the multiplier LT dma/ind : mem -> TREG0 LTA dma/ind : load T, ACC=ACC+P LTD dma/ind : load T, ACC=ACC+P,move data LTP dma/ind : load T, P->ACC

Characteristics of TI ‘C5x DSPs

Switchable between Data & Program memory