sharc dsp 学习记录1---2014-07-30
从今天开始记录学习sharc dsp过程中的点点滴滴吧。
DPI：Digital Peripheral Interface
DAI：Digital Audio Interface
SHARC SIMD Core
SIMD 单指令多数据
ADSP-2148x包含两个用作单指令、多数据(SIMD)引擎的计算处理器元件，分别称为PEX和PEY，各元件均由ALU、乘法器、移位器和寄存器文件组成。
PEX始终有效，PEY可通过将MODE1寄存器的PEYEN模式位设为1来使能。SIMD模式允许处理器在两个处理元件中执行同一指令，但各处理元件处理不
同的数据。这种架构对于执行计算密集型DSP算法非常有效
SIMD Enabled:
When any computation or data access is executed, it will be performed automatically in both processing elements
F0 = F1 + F2; explicitly defined in source code Will execute in PEx
S0 = S1 + S2; implicit operation not defined in source code Will be automatically executed in PEy in the same instruction cycle
SIMD Disabled (SISD Mode):
Only the explicit instruction will be executed in PEx
PM地址总线的宽度 = 24bits 。可最多访问16Mbit的程序/数据。
PM数据总线的宽度 = 48bits。 用以存取48 位字长的指令，当用来存放数据时，32 位单精度浮点数或32位定点数将位于48 位的高32 位中
48位指令字支持各种并行操作，可实现简练编程。例如，处理器可以有条件地在两个处理元件中执行乘法、加法和减法，同时进行分支并从存储
器获取最多4个32位数据值，所有这些只需一个指令。
汇编程序分析（FIR）
#include "def21364.h" /* Symbol Definition File */#define TAPS 64 /* length of filter */
#define N 128 /* number of samples */.extern ss_fir;
/* DM data */
.section/dm seg_dmda; /* Segments are declared in the .ldf file*/
.ALIGN 2; /* Set alignment to long-word boundary for next variable */
.var dline[TAPS+1]; /* delay line compensate for circ buffer, see comments in SS_FIR.asm */
.ALIGN 2;
.var input[N] = "input.dat"; /* array of samples */
/* PM data */
.section/dm seg_pmda;
.ALIGN 2;
.var coeffs[TAPS] = "ssfcoeffs.dat"; /* Filter coefficients */
.ALIGN 2;
.var output[N]; /* Output array */
/* PM interrupt vector code */
.section/pm seg_rth;
Reserved_1: rti; nop; nop; nop;
Chip_Reset: idle; jump start; nop; nop;
/* program memory code */
.segment/pm seg_pmco;start:
/*--------------------- Setup modify registers for arrays --------------------*/
m1 = 1;
m2 = -1;
m3 = 2;m9 = 2;
m10= 1;
/*----------------------------------------------------------------------------*/
/*--------------------- Initialization delay line ----------------------------*/
b0 = dline;
l0 = @dline-1;f8=0.0;
lcntr = TAPS, do clear_fir until lce;
clear_fir: dm(i0,m1) = f8;i0 = dline;
/*----------------------------------------------------------------------------*/
/*-------------- Setup DAGs for input/output/coeffs and call ss_fir ----------*/
r3 = TAPS;
r3 = lshift r3 by -1; /* r3 = taps/2 due to SIMD mode */
r0 = 3; /* 3 macs outside of fir mac loop */
r3 = r3 - r0; /* r3 = taps/2 - 3 for fir mac loop counter */
b1 = input;
l1 = 0;b9 = output;
l9 = 0;b8 = coeffs;
l8 = @coeffs;
lcntr = N, do fir_loop until lce;
call ss_fir (db); /* Call fir */
f0 = dm(i1,m1); /* Read one sample */
nop; /* Call can't be in last three locations of a loop */
fir_loop: pm(i9,m10)=f8; /* Write result to output */
/*----------------------------------------------------------------------------*/
/* Terminate and wait */
wait1: idle;
jump wait1;
#include "def21364.h" /* Symbol Definition File */
.global ss_fir;
/* program memory code */
.section/pm seg_pmco;ss_fir:
bit set MODE1 CBUFEN; /* Circular Buffer Enable, one cycle effect latency */
nop; /* Circular Buffering not in effect until next cycle */
s0 = dm(i0, m1); /* move pointer to delay[1] */
bit set MODE1 PEYEN; /* SIMD Mode Enable, one cycle effect latency */
s0 = dm(i0, m2); /* load s0 with the value of delay[1] for SIMD store, move pointer to delay[0] */
dm(i0,m3)=f0, f4 = pm(i8,m9); /* transfer sample to delayline, done in SIMD to load end of buffer + 1 */
/* to compensate for circular buffer issue described above, read 2 coeffs */f8=f0*f4, f0=dm(i0,m3), f4=pm(i8,m9); /* samples * coeffs, read 2 samples, read 2 coeffs */
f12=f0*f4, f0=dm(i0,m3), f4=pm(i8,m9); /* samples * coeffs, read 2 samples, read 2 coeffs */
lcntr=r3, do macs until lce; /* FIR loop */
macs:f12=f0*f4, f8=f8+f12, f0=dm(i0,m3), f4=pm(i8,m9); /* samples * coeffs, accum, read 2 samples, read 2 coeffs */
f12=f0*f4, f8=f8+f12, s0=dm(i0,m2); /* samples * coeffs, accum, dummy read to move pointer to oldest sample */
f8=f8+f12; /* final SIMD accum */
r12=s8; /* move PEy total into PEx register file */
rts (db);
bit clr MODE1 CBUFEN | PEYEN; /* Circular Buffer Disable, SIMD Mode Disable */
f8=f8+f12; /* last accum */
dline的读写
红色表示进入macs 循环前 i0指针指向的位置。
该程序使用了循环寻址的方式
Bx、Lx、Ix 三个寄存器的序号x 必须一致，而Mx 寄存器可以在同一个DAG 组中任意选取
R3 = lshift R3 by -1； //右移1bit
