Setting the PTG Output Trigger Pulse Width

Last modified by Microchip on 2023/11/09 09:00

The PTGTRIG Step Command causes the Peripheral Trigger Generator (PTG) to generate one of the 32 trigger signals (PTGO0 - PTG3O1). These signals are used as control inputs to other MCU peripherals synchronizing activity. PTG trigger signals can be configured in one of the two modes:

  • In Toggle mode, the current value of the trigger signal will be toggled when PTGTRIG is executed.
  • In Pulse mode, PTGTRIG will trigger a one-time pulse on PTGOx. Here, the width of the pulse is set by the application program.

The different trigger modes of the PTG - toggle and pulse

Selecting the Trigger Mode

The mode of the Trigger signal is determined by the Toggle Output Mode bit in the PTG Control and Status Register (PTGCST<12>).

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PTGCST: PTG Status and Control Register

The PTGTOGL bit in the PTG Status and Control Register controls the trigger output mode - toggle or pulse

bit 12

PTGTOGL: TRIG Output Toggle Mode bit

1 = Toggle the state of PTGOx on each PTGTRIG command
0 = Generate a single pulse on PTGOx on each PTGTRIG command

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Determining the Pulse Width of the Trigger

When Trigger Pulse mode is selected, the width of the pulse is determined by a field in the PTG Control Register (PTGCON<7:4>).

PTGCON: PTG Control Register

The four PTGWDT bits in the PTGCON register control the pulse width of the trigger pulse output

bit 7 - 4

PTGPWD<3:0>: PTG Trigger Output Pulse Width bits

1111 = All triggers are 16 PTG clock cycles
1110 = All triggers are 15 PTG clock cycles

0001 = All triggers are 2 PTG clock cycles
0000 = All triggers are 1 PTG clock cycles

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Example Code

// include the XC header file to define all register and bit names
#include <xc.h>

//  Setting the PTG the Toggle mode
PTGTOGL = 1;  // Set for Toggle Mode

// Setting the PTG for a Pulse width of 3 PTG clocks
PTGEN = 0;    // PTGCON can only be written with PTGEN = 0
PTGPWD = 2;   // Set pulse width to 3
PTGTOGL = 0;  // set for pulse mode

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