Demo: Experiment with FRQA / PHSA regiser in POS detector mode

Reinhard · 2011-11-10 12:35

/*
    Experiment with Low Level Register Access 
    
    reimay        11.10.2011
    
    propeller-elf-gcc   -mlmm -o counter.elf  -Os counter.c 

*/

#include <stdio.h>
#include <propeller.h>

// for this experiment connect P0 with P1 !!!
#define P1 1<<1
#define P0 1<<0

// POS detector mode, accumulate FRQA to PHSA if P1 (input) = H
#define CRTMODE (1<<29) + 1  



void main ()
{
LOOP:
    getchar();                        // wait for any serial input
    
    DIRA |= P0;                        // P0 = OUTPUT
    OUTA &= ~P0;                    // P0 = LOW
    
    CTRA = CRTMODE;                    // set Counter Module
    FRQA = 1;                        // set FRQA Register := 1
    
    PHSA = 0;                        // clear PHSA Register
    
    OUTA |= P0;                        // P0 = HIGH; connected with P1 -> accumalate FRQA to PHSA
    waitcnt(CNT + CLKFREQ/1000);    // wait 1 ms
    OUTA &= ~P0;;                    // P0 = LOW; stop accumulator
    
    printf("%d\n",PHSA);            // send content of PHSA : result = 80112 ; 1ms = 80000 clocks @ 80 MHz + 112 clocks for VM
                                    // without -Os we have 752 clocks for VM, try it
    goto LOOP;
    
}
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jazzed · 2011-11-10 18:56

It's good to experiment with counters like this. Counter's are one of Propeller's strengths.

Demo: Experiment with FRQA / PHSA regiser in POS detector mode

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