C166: How to Load PEC Registers of XC16X Devices
Information in this article applies to:
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
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 split this up to a segment number and 16-bit
The following example program should demonstrate this. It
transmits a string out the serial port using PEC channel 0.
#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 )) - 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
// 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));
PSW_IEN = 1; // Enable interrupts
void main (void)
serial_setup (19200); // setup serial interface for 19200 baud
Refer to _sof_
in the C166 User's Guide.
Last Reviewed: Thursday, February 25, 2021