External Windowed Watchdog with MPC5554

[gmgunderground]

I have to refresh an external windowed watchdog through pin GPIO203(EMIOS14) and the wave form must be as reported in the attached images. What is the best way to generate it? Someone has an example? If I'm not wrong EMIOS can generate continuously wave forms without main core interaction, is right?

best regards

Gian

[lukaszadrapa]

Hi,

yes, EMIOS can be used for this. See the example for OPWM mode in application note AN2865:

http://www.freescale.com/files/32bit/doc/app_note/AN2865.pdf

MPC5500 and MPC5600 Simple Cookbook Code

Regards,

Lukas

[gmgunderground]

Tank you, is the same documentation I have just found. But I think I'm making something wrong, I can't make the desired signal. This is my code, do you see something wrong? MPC5554 is running at 80 MHz. I need 135ms LOW and 30ms HIGH as reported in the previous post

void initEMIOS(void)

{

  EMIOS.MCR.B.GPREN = 0; // Enable eMIOS clock

  EMIOS.MCR.B.GPRE= 79; // Divide 80 MHz sysclk by 79+1 = 80 for 1MHz eMIOS clk

  EMIOS.MCR.B.ETB = 0; // External time base is disabled; Ch 23 drives ctr bus A

  EMIOS.MCR.B.GTBE = 1; // Enable global time base

  EMIOS.MCR.B.FRZ = 0; // Enable stopping channels when in debug mode

  EMIOS.MCR.B.GPREN = 1; // Enable eMIOS clock

}

void initEMIOSch23(void)

{ // EMIOS CH 23: Modulus Up Counter

  EMIOS.CH[23].CADR.R = 999; // Period will be 999+1 = 1000 clocks (1 msec)

  EMIOS.CH[23].CCR.B.MODE = 0x10;// MPC555x: Modulus Counter (MC)

  EMIOS.CH[23].CCR.B.BSL = 0x3; // Use internal counter

  EMIOS.CH[23].CCR.B.UCPRE=0; // Set channel prescaler to divide by 1

  EMIOS.CH[23].CCR.B.FEN = 0;

  EMIOS.CH[23].CCR.B.FREN = 0; // Freeze channel counting when in debug mode

  EMIOS.CH[23].CCR.B.UCPREN = 1; // Enable prescaler; uses default divide by 1

}

void initEMIOSch14(void)

{

  // EMIOS CH 14: Output Pulse Width Modulation

  EMIOS.CH[14].CADR.R = 130;

  EMIOS.CH[14].CBDR.R = 165;

  EMIOS.CH[14].CCR.B.BSL = 0x0; // Use counter bus A (default)

  EMIOS.CH[14].CCR.B.EDPOL = 1; //Polarity-leading edge sets output/trailing clears

  EMIOS.CH[14].CCR.B.MODE = 0x20; // MPC555x: Mode is OPWM

  SIU.PCR[203].B.PA = 1;

  SIU.PCR[203].B.OBE = 0;

  SIU.PCR[203].B.IBE = 0;

  SIU.PCR[203].B.ODE = 0;

  SIU.PCR[203].B.HYS = 0;

  SIU.PCR[203].B.SRC = 0;

  SIU.PCR[203].B.WPE = 0;

  SIU.PCR[203].B.WPS = 0;

}