C166: HOW TO LOAD PEC REGISTERS OF XC16X DEVICES

Information in this article applies to:

• C166 all Versions

QUESTION

The PEC registers of Infineon XC16x devices need to be loaded with addresses of variables and SFR's. How can I separate an address into a segment number and a 16-bit offset to load these PEC source and destination registers?

ANSWER

The library function _sof_ and a cast can be used for this. These expressions convert any address (near,far,idata,sdata etc.) into a linear address and splits this up to a segment number and 16-bit segment-offset.

The following example program should demonstrate this. It transmits a string out the serial port using PEC channel 0.

#include <XC167.H>
#include "intrins.h"

#define CLOCK 20000000UL // CPU clock when PLL is enabled

const char string1 [] = "0123456789\n";

#define _seg_(adr) (unsigned int)(((unsigned long)(void huge *)adr) >> 16)

// This function initializes PEC Channel 0 to move the data from
// 'string1' to the serial transmit buffer.

void serial_PEC0_setup (void)
{
  PECC0   = 0x0500 |                  // Move Bytes, Inc Src Ptr
            ((sizeof (string1) / sizeof (string1 [0])) - 1);
  SRCP0   = _sof_ (string1);          // Source is 'string1'
  DSTP0   = _sof_ (&ASC0_TBUF);       // Destination is ASC transmit buffer
  PECSEG0 = (_seg_ (string1) << 8) |  // high byte = Segment of Source
            (_seg_ (&ASC0_TBUF));     // low byte  = Segment of Destination
}


// The Serial TX interrupt just reloads PEC 0 and starts the transfer of
// another copy of 'string1'.

void serial_TX_irq (void) interrupt S0TINT = 42
{
  serial_PEC0_setup ();
}

// The setup routine for the serial port also initialized the PEC 0
// transfer and sets a TX interrupt request

void serial_setup (unsigned int baudrate)
{
  DP3       |=  0x0400;   // Set TXD for output
  DP3       &= ~0x0800;   // Set RXD for input
  P3        |=  0x0400;   // Set TXD high
  ALTSEL0P3 |= 0x0C00;    // Configure port pins for ASC0
  ASC0_CON   = 0x8011;    // 8 bit async mode
  ASC0_TIC   = 0x00F8;    // Serial TX IRQ = Level 14, Priority 0 (PEC 0)

  ASC0_BG  = (unsigned int)(CLOCK / (32UL * (unsigned long) baudrate));

  serial_PEC0_setup ();

  PSW_IEN = 1;            // Enable interrupts
}


void main (void)
{
  serial_setup (19200);   // setup serial interface for 19200 baud

  while (1)
  {
  }
}

MORE INFORMATION

• Refer to _sof_ in the C166 User's Guide.

SEE ALSO

• C166: HOW TO GET 16-BIT ADDRESSES INTO THE PEC REGISTERS?

Last Reviewed: Monday, March 5, 2007