--- title: How to pause in PASM description: "[PASM](https://obex.parallax.com/code-language/pasm/), [SPIN](https://obex.parallax.com/code-language/spin/) #### Introduction These code snippets put together some previous tips to demonstrate how to pause and toggle pins with PASM! The examples here are deliberately verbose and include comments to describe each line of code, but if you…" url: "https://obex.parallax.com/docs/chips-tips/propeller-1/how-to-pause-in-pasm/" updated: "2025-04-28" category: Propeller 1 --- # How to pause in PASM [PASM](https://obex.parallax.com/code-language/pasm/), [SPIN](https://obex.parallax.com/code-language/spin/) #### Introduction These code snippets put together some previous tips to demonstrate how to pause and toggle pins with PASM! The examples here are deliberately verbose and include comments to describe each line of code, but if you have any questions please reach out at our [forums](#resources)! The code assumes you are using the Parallax Propeller FLiP module, or the Parallax Propeller Activity Board. We toggle the LEDs that are included in those boards as a simple way of demonstrating the pause duration. Simply copy/paste this code into your favourite Propeller SPIN compiler, then load the code into your Propeller 1! #### Example code - milliseconds This code includes a milliseconds pause routine, so it will allow you to create pauses long enough to be visually identified by the LEDs flashing on and off! ```spin CON { System timing } _XINFREQ = 5_000_000 _CLKMODE = XTAL1 + PLL16X CON { IO Pins - Assumes FLiP module or Propeller Activity Board } LEDA = 26 LEDB = 27 ' ---------------------------------------------------------------------------------------------------- PUB start ' Initialization MS_TICKS := clkfreq / 1_000 ' Pre-calculate the ticks duration of 1mS based on system clock LEDA_mask := |< LEDA ' Create mask representing the LEDA pin number LEDB_mask := |< LEDB ' Create mask representing the LEDB pin number dira[LEDA]:= 0 ' Float pins before passing to cog dira[LEDB]:= 0 ' - not essential in this demo as the pins had not been used yet! cognew(@PauseDemo,0) ' Start the pause demo code running in 2nd processor cog repeat ' Repeat here doing nothing waitcnt(0) ' - in real code, you'd probably do something here! ' ---------------------------------------------------------------------------------------------------- DAT { PASM - PauseDemo } PauseDemo org 0 ' Begin at Cog RAM addr 0 or dira, LEDA_mask ' Set pin to output or outa, LEDA_mask ' Set pin to high or dira, LEDB_mask ' Set pin to output andn outa, LEDB_mask ' Set pin to low (default state - just showing how to do it!) demoloop mov msecs, #125 ' Set 125mS pause call #pausems ' Call pause routine; returns here when done xor outa, LEDA_mask ' Toggle state of pin LEDA xor outa, LEDB_mask ' Toggle state of pin LEDB jmp #demoloop ' Jump back to loop label; ie. start again! ' --------------------- ' Pause in milliseconds ' --------------------- ' ' Example use: ' mov msecs, #100 ' set 100mS pause ' call #pausems pausems mov mstimer, MS_TICKS ' set timer for 1ms add mstimer, cnt ' sync with system clock msloop waitcnt mstimer, MS_TICKS ' wait and reload djnz msecs, #msloop ' update delay count pausems_ret ret ' PASM / Global Variables MS_TICKS long 0-0 ' ticks per ms LEDA_mask long 0-0 LEDB_mask long 0-0 msecs res 1 mstimer res 1 FIT ' DAT PASM - PauseDemo ' ---------------------------------------------------------------------------------------------------- ``` LEDs A and B will toggle on/off with a 125 millisecond pause between each change. --- #### Example code - microseconds This version of the demo code includes a microseconds pause routine. The pause is so short that the two LEDs will appear to be always ON! But with an oscilloscope you will be able to measure and view the 150uS pulses. ```spin CON { System timing } _XINFREQ = 5_000_000 _CLKMODE = XTAL1 + PLL16X CON { IO Pins - Assumes FLiP module or Propeller Activity Board } LEDA = 26 LEDB = 27 ' ---------------------------------------------------------------------------------------------------- PUB start ' Initialization US_TICKS := clkfreq / 1_000_000 ' Pre-calculate the ticks duration of 1uS based on system clock LEDA_mask := |< LEDA ' Create mask representing the LEDA pin number LEDB_mask := |< LEDB ' Create mask representing the LEDB pin number dira[LEDA]:= 0 ' Float pins before passing to cog dira[LEDB]:= 0 ' - not essential in this demo as the pins had not been used yet! cognew(@PauseDemo,0) ' Start the pause demo code running in 2nd processor cog repeat ' Repeat here doing nothing waitcnt(0) ' - in real code, you'd probably do something here! ' ---------------------------------------------------------------------------------------------------- DAT { PASM - PauseDemo } PauseDemo org 0 ' Begin at Cog RAM addr 0 or dira, LEDA_mask ' Set pin to output or outa, LEDA_mask ' Set pin to high or dira, LEDB_mask ' Set pin to output andn outa, LEDB_mask ' Set pin to low (default state - just showing how to do it!) demoloop mov usecs, #150 ' Set 150uS pause call #pauseus ' Call pause routine; returns here when done xor outa, LEDA_mask ' Toggle state of pin LEDA xor outa, LEDB_mask ' Toggle state of pin LEDB jmp #demoloop ' Jump back to loop label; ie. start again! ' --------------------- ' Pause in microseconds ' --------------------- ' ' Example use: ' mov usecs, #9 ' set 9uS pause ' call #pauseus pauseus mov ustimer, US_TICKS ' set timer for 1us add ustimer, cnt ' sync with system clock usloop waitcnt ustimer, US_TICKS ' wait and reload djnz usecs, #usloop ' update delay count pauseus_ret ret ' PASM / Global Variables US_TICKS long 0-0 ' ticks per us LEDA_mask long 0-0 LEDB_mask long 0-0 usecs res 1 ustimer res 1 FIT ' DAT PASM - PauseDemo ' ---------------------------------------------------------------------------------------------------- ``` LEDs A and B will toggle on/off with a 150 microsecond pause between each change. This will be too fast for the human eye, but you will be able to read the pulses with an oscilloscope. --- ## Resources [Parallax Community Forums](https://forums.parallax.com) [Parallax Propeller 1 Manual](https://www.parallax.com/package/propeller-manual) [Parallax Propeller 1 Documentation](https://www.parallax.com/download/propeller-1-documentation) --- ## Download > [How to pause in PASM](https://obex.parallax.com/obex/how-to-pause-in-pasm/) [“How to pause in PASM” — Propeller OBEX](https://obex.parallax.com/obex/how-to-pause-in-pasm/embed/#?secret=fKG1tWTYtk#?secret=qIHMUyZZWK)