Hello all,
Currently I am exploring VLG-S12zvca evaluation board. Working on 16bit timer.
I have written a small code where I am toggling GPIO pin PP6 and varying its on and off timing by using 16 bit timer, I have set ECLK to 24 MHz. i have observed following observations and Also please find attached doc for reference.
Questions:-
1) if we increment timer counter to maximum value that is 65535 and set prescalar value to 0 , it generates 2.73msec of delay, observed at ppg, it matched with calculations as mentioned below -->
Delay time = Counter value/ Eclk/2^ prescalar value
= 65535/24/2^0 * 10^-6
= 65535/24 us
=2730.625 us
=2.73ms
I want to know that , how much minimum delay can be generated using minimum counter value ?
2) I have checked for counter value 1,2,3,4,5 it consider as 65535 and generates 2.73msec of delay it doesn't matches with calculations o, instead I have observed 1us of delay at counter value of 6, why is it?
| Sr.no. | ON time Value | Off time value | Observed ON time Value | Observed Off time Value | Calculated on(us) | Calculated off(us) |
| 1 | 65535 | 65535 | 2.8ms | 2.8ms | 2730.625 | 2730.625 |
| 2 | 10000 | 65535 | 420us | 2.76ms | 416.6666667 | 2730.625 |
| 3 | 1 | 65535 | 2.76ms | 2.76ms | 0.041666667 | 2730.625 |
| 4 | 2 | 65535 | 2.76ms | 2.76ms | 0.083333333 | 2730.625 |
| 5 | 3 | 65535 | 2.76ms | 2.76ms | 0.125 | 2730.625 |
| 6 | 4 | 65535 | 2.76ms | 2.76ms | 0.166666667 | 2730.625 |
| 7 | 5 | 65535 | 2.76ms | 2.76ms | 0.208333333 | 2730.625 |
| 8 | 6 | 6 | 1us | 1us | 0.25 | 0.25 |
--> Does it mean that S12zvca internally takes 24cycles for its compiling, boot loading or any other tasks that's why it supports only 1us at counter value 6?
-->is it possible to generate a delay in nanosecond by using s12zvca ? if yes then how?
Also Find code below;-
#include <hidef.h> /* for EnableInterrupts macro */
#include "derivative.h" /* include peripheral declarations */
void main(void) {
CPMUCLKS_PLLSEL = 1;
CPMUREFDIV_REFFRQ = 1;
CPMUREFDIV_REFDIV = 0x0;
CPMUSYNR_VCOFRQ = 0x1;
CPMUSYNR_SYNDIV = 0x5;
CPMUPOSTDIV_POSTDIV = 0x0;
CPMUOSC_OSCE = 1;
while(!CPMUIFLG_LOCK){}
CPMUIFLG = 0xFF;
ECLKCTL_NECLK=0;
//Use PP6 as output for LED
DDRP_DDRP6 = 1;
TIM0TSCR1 = 0x90;
TIM0TSCR2 = 0x10;
TIM0TIOS_IOS0=1;
for(;;){
PTP_PTP6=1;
TIM0TC0 = TIM0TCNT + 65535 ; /* start an OC0 operation_300ms */
while(!(TIM0TFLG1 & 0x01)); /* wait for PT0 to go high */
PTP_PTP6=0;
TIM0TC0 = TIM0TCNT + 65535 ; /* start an OC0 operation_300ms */
while(!(TIM0TFLG1 & 0x01)); /* wait for PT0 to go high */
}
}
Please let me know your all valuable comments and suggestion.
Thank You,
Shubhangi Mahajan
