cpux_03.c

Extended Memory Access Using IAR v3.42A and CCE v2

//******************************************************************************
//  MSP430xG461x Demo - DMA0, Single Blk to RAM Memory location, Software ptr, 
//                      Rpt'd Blk from RAM to DAC0, Sine Out, TimerA0, DCO
//
// This program shows how a look-up table placed in the extended memory is 
// moveded as a block to the RAM using DMA and then moved word by word from RAM
// to DAC via a 16-bit address variable.
//
// Description: A 32 word Sine look-up table is stored in the extended memory 
// location 0x10000 onwards by interfacing C with assembly code. A 32-bit 
// address variable is used to access the data from the extended memory and 
// transfer the contents of the Sine look-up table word-by-word as a repeating 
// block to DAC12_0. And DAC12_0 outputs on P6.6 a 1-kHz Sine wave. Timer A 
// operates in compare mode, where, TACCR0 sets the Clock period and TACCR1 sets 
// the PWM duty cycle. To get a 1-kHz Sine wave out, Timer period is
// set to almost 32us (as 32us*32 words ~ 1ms) , with TimerA clock  running at 
// 1MHz. And during the TimerA0 ISR the data present at the address pointed by 
// the addr variable then is loaded to the DAC12_0DAT register for conversion 
// and the addr variable is incremented to point the next address.  
// DAC12_0 uses internal 1.5V reference.
// ACLK = 32kHz, MCLK = SMCLK = default DCO 8MHz, TACLK = SMCLK/8 = 1MHZ
//
//                MSP430xG461x
//             -----------------
//         /|\|              XIN|-
//          | |                 | 32kHz
//          --|RST          XOUT|-
//            |                 |
//            |        DAC0/P6.6|--> ~ 1-kHz sine wave output
//
//   Note 1: The linker command file for this project has to be modified to  
//           create a new memory segment (CONST_HIGH - in this example). The  
//           linker command -Z(CONST)CONST_HIGH=10000-1FFFF is used to create  
//           a new memory segment in the extended memory (0x10000 - 0x1FFFF).
//   Note 2: This code example interfaces C with Assembler code, therefore, the 
//           project must include assembly file "ASM_func.s43".
//
//   Bhargavi Nisarga
//   Texas Instruments Inc.
//   June 2007
//   Built with IAR Embedded Workbench Version: 3.42A
//******************************************************************************

#include "msp430xG46x.h"
#include "intrinsics.h"

/* The variable "Buffer" allocates 32 words in RAM; the 32 word sine wave table
 is transferred from the extended flash to this location*/
unsigned int Buffer[32];                    
extern unsigned long __Get_Address20(void); // Func prototype for ASM func 
unsigned int *Pointer;                      // 16-bit Pointer
unsigned short Count, Size;

void main(void)
{
  volatile unsigned int i;
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer
  //Set DCO freq = 8MHz
  FLL_CTL0 |= DCOPLUS + XCAP18PF;           // DCO+ set, freq = xtal x D x N+1
  SCFI0 |= FN_4;                            // x2 DCO freq, 8MHz nominal DCO
  SCFQCTL = 121;            
  
  ADC12CTL0 = REFON;                        // Internal 1.5V reference
  for (i = 0x3600; i; i--);                 // Delay for needed ref start-up.
                                            // See datasheet for details.
  
  // Configure DMA0  - block transfer on software request
  DMACTL0 = DMA0TSEL_0;                     // DMA_REQ (sw)
  __data16_write_addr ((unsigned short)&DMA0SAL, __Get_Address20());
                                            // Source address = Extended Flash
  DMA0DAL = (unsigned int)&Buffer;          // Destination addr = RAM location
  DMA0SZ = 0x20;                            // Size in words
  DMA0CTL = DMADT_1 + DMADSTINCR_3 + DMASRCINCR_3 + DMAREQ + DMAEN; 
                                            // Blk transfer, src & dest incr, 
                                            // DMA_REQ(sw), enable DMA
  
  // Initialize Pointer to point to the starting address of data table in RAM 
  Pointer = (unsigned int *)&Buffer;           
  Size = 0x0020;                            // Size in words
  Count = 0;
  
  // Configur DAC12_0  
  DAC12_0CTL = DAC12IR + DAC12AMP_5 + DAC12ENC;
                                            // amp and i/p range setting, 
                                            // DAC enable  
  
  // Configure Timer A
  TACCTL1 = OUTMOD_3;                       // TACCR1 set/reset 
  TACCR1 = 1;                               // TACCR1 PWM Duty Cycle
  TACCR0 = 30;                              // Clock period of TACCR0
  TACCTL0 = CCIE;                           // Interrupt enable
  TACTL = TASSEL_2 + MC_1 + TACLR + ID_3;   // SMCLK, upmode, (i/p clk/8)
  
  __bis_SR_register(LPM0_bits + GIE);       // Enter LPM0, enable interrupts
}

// TimerA interrupt service routine
#pragma vector = TIMERA0_VECTOR
__interrupt void TA0_ISR(void)
{
    /* Data located at the address pointed by the Pointer is loaded to DAC data
    register and is word incremented to point the next word in RAM memory */
    DAC12_0DAT = *Pointer++;                 
    if (++Count >= Size)                    // Chk if Count within memory range
    {
      // Repeat Blk transfer from RAM to DAC12_0
      Pointer = (unsigned int *)&Buffer;      
      Count = 0;
    }
}