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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| PIC16F1455 clock too slow, please help |
 Posted: Wed Jun 25, 2014 8:29 am |
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Hello, I need my PIC to run at 48MHz. So to test the speed I made this code:
| Code: |
#include <16F1455.h>
#FUSES NOWDT //No Watch Dog Timer
#FUSES INTRC_IO //Internal RC Osc, no CLKOUT
#FUSES WDT_SW //No Watch Dog Timer, enabled in Software
#FUSES NOMCLR //Master Clear pin used for I/O
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOIESO //Internal External Switch Over mode disabled
#FUSES NOFCMEN //Fail-safe clock monitor disabled
#FUSES NOSTVREN //Stack full/underflow will not cause reset
#FUSES BORV25 //Brownout reset at 2.5V
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCLKOUT
#FUSES NOCPUDIV
#FUSES PLLEN
#FUSES PLL3X
#use delay(clock=48000000)
void main() {
long i, j;
output_high(PIN_C1);
while(TRUE){
for(i=0;i<3464;i++){
for(j=0;j<3464;j++){
}
}
output_toggle(PIN_C1);
}
}
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There is a LED on PIN_C1, but it takes 12 second to toggle. The loop is 12 million long, so if my calculations are correct it should toggle every second. It appears that the PIC is running at 4MHz, not 48.
Could anyone correct me if I'm wrong? I need to know if the clock speed is correct.
Thank you in advance. |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Posted: Wed Jun 25, 2014 9:05 am |
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Hi,
Try this substitution:
| Code: |
#use delay(internal=48000000)
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John |
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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| Posted: Wed Jun 25, 2014 9:08 am |
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Thank you for your quick response John.
I did it already, still 12 seconds :/ |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Posted: Wed Jun 25, 2014 9:16 am |
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Hi,
Admittedly, I don't use that PIC (or any quite like it), but here is what I would try next:
| Code: |
#use delay(internal=16000000, clock=48000000)
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That PIC has a 16MHz internal oscillator, and with the PLL can achieve 48MHz internally. your problem is just a matter of sorting out the correct way to get that setup properly.
John |
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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| Posted: Wed Jun 25, 2014 9:21 am |
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| Nothing, still 12 seconds |
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temtronic
Joined: 01 Jul 2010
Posts: 9221
Location: Greensville,Ontario
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| Posted: Wed Jun 25, 2014 9:27 am |
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hmm... compiler version bug ??
I'd printout the listing to check what the fuse REALLY are,not what we 'think' they are.
Also I'd use a
delay_ms(500);
output_toggle(LED);
instead of the loopy-loop , at least for a sanity check....
hth
jay |
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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| Posted: Wed Jun 25, 2014 9:37 am |
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Here is what the listing says:
| Code: |
CCS PCM C Compiler, Version 4.140, 5967 25-jun-14 17:19
Filename: C:\Users\Jose Carlos\Desktop\Camara Termica\Programa16F\infrarrojos.lst
ROM used: 61 words (1%)
Largest free fragment is 2048
RAM used: 9 (1%) at main() level
20 (2%) worst case
Stack: 0 locations
*
0000: MOVLP 00
0001: GOTO 003
0002: NOP
.................... #include <16F1455.h>
.................... #device PIC16F1455
.................... #list
....................
....................
.................... #FUSES NOWDT //No Watch Dog Timer
.................... #FUSES INTRC_IO //Internal RC Osc, no CLKOUT
.................... #FUSES WDT_SW //No Watch Dog Timer, enabled in Software
.................... #FUSES NOMCLR //Master Clear pin used for I/O
.................... #FUSES NOBROWNOUT //No brownout reset
.................... #FUSES NOIESO //Internal External Switch Over mode disabled
.................... #FUSES NOFCMEN //Fail-safe clock monitor disabled
.................... #FUSES NOSTVREN //Stack full/underflow will not cause reset
.................... #FUSES BORV25 //Brownout reset at 2.5V
.................... #FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
.................... #FUSES NOCLKOUT
.................... #FUSES NOCPUDIV
.................... #FUSES PLLEN
.................... #FUSES PLL3X
....................
.................... #use delay(internal=16000000, clock=48000000)
....................
....................
....................
.................... void main() {
0003: CLRF 05
0004: CLRF 04
0005: MOVLW 3C
0006: MOVLB 01
0007: MOVWF 19
0008: CLRF 18
0009: MOVLB 03
000A: CLRF 0C
000B: CLRF 0E
000C: MOVLB 02
000D: CLRF 12
000E: CLRF 11
000F: CLRF 14
0010: CLRF 13
.................... long i, j;
.................... output_high(PIN_C1);
0011: MOVLB 01
0012: BCF 0E.1
0013: MOVLB 02
0014: BSF 0E.1
.................... while(TRUE){
.................... for(i=0;i<3464;i++){
0015: MOVLB 00
0016: CLRF 22
0017: CLRF 21
0018: MOVF 22,W
0019: SUBLW 0D
001A: BTFSS 03.0
001B: GOTO 036
001C: BTFSS 03.2
001D: GOTO 022
001E: MOVF 21,W
001F: SUBLW 87
0020: BTFSS 03.0
0021: GOTO 036
.................... for(j=0;j<3464;j++){
0022: CLRF 24
0023: CLRF 23
0024: MOVF 24,W
0025: SUBLW 0D
0026: BTFSS 03.0
0027: GOTO 032
0028: BTFSS 03.2
0029: GOTO 02E
002A: MOVF 23,W
002B: SUBLW 87
002C: BTFSS 03.0
002D: GOTO 032
.................... }
002E: INCF 23,F
002F: BTFSC 03.2
0030: INCF 24,F
0031: GOTO 024
.................... }
0032: INCF 21,F
0033: BTFSC 03.2
0034: INCF 22,F
0035: GOTO 018
.................... output_toggle(PIN_C1);
0036: MOVLB 01
0037: BCF 0E.1
0038: MOVLW 02
0039: MOVLB 02
003A: XORWF 0E,F
.................... }
003B: GOTO 015
.................... }
003C: SLEEP
Configuration Fuses:
Word 1: 098C INTRC_IO WDT_SW PUT NOMCLR NOPROTECT NOBROWNOUT NOCLKOUT NOIESO NOFCMEN
Word 2: 19CF NOWRT NOCPUDIV LS48MHZ PLL3X PLLEN NOSTVREN BORV25 NOLPBOR NODEBUG NOLVP
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The configuration words are set correctly (I have checked the datasheet), but it seems that the OSCTUNE is not set anywhere to the max frecuency.
So my guess is that the PIC is running at the HFINTOSC default after-reset speed, which is 500kHz, with PLLx3 = 1.5MHz. Wich makes total sense with the speed I'm seeing.
The problem is, I don't know how to do it by myself, I have tried but with no results. |
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jeremiah
Joined: 20 Jul 2010
Posts: 1345
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| Posted: Wed Jun 25, 2014 10:27 am |
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With the code you had, I calculate a 12ish second delay between each toggle.
Inner loop
You have roughly 12 instructions executed 3464 times = 41,568 instructions
Outer loop
You have roughly (13 instructions + inner loop ) * 3464 = 144,036,584 instructions
At 48 MHz, the instruction clock is 48/4 = 12 MHz
144,036,584 instructions at 12 MHz is 12 seconds
Note, that is rough calcs. I didn't check individual instruction times or do one offs on the loop, so this is just approximate
Did you try the delay_ms() method mentioned earlier?
Last edited by jeremiah on Wed Jun 25, 2014 10:37 am; edited 1 time in total |
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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| Posted: Wed Jun 25, 2014 10:32 am |
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Jeremiah, could you please explain to me why there are these number of instructions?
Thank you. |
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jeremiah
Joined: 20 Jul 2010
Posts: 1345
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| Posted: Wed Jun 25, 2014 10:35 am |
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For loops aren't single instructions. They have things like subtractions, comparisons, increments, branching, etc. It takes a lot of instructions. Your counts would be fine if a for loop could be executed in a single instruction, but that's not currently possible in any architectures out there that I have heard of.
Just think each loop has to check the loop count, increment it, compare it, and then decide to continue the loop or leave it after the comparison. That all takes a certain amount of instructions (time). |
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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| Posted: Wed Jun 25, 2014 10:44 am |
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I understand, also I didn't notice that "i" and "j" are long int (16bit), so for a 8bit PIC takes double the time to process...
Thank you. |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Posted: Wed Jun 25, 2014 10:55 am |
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Hi,
So, it's working now?
In addition to the lesson of keeping your test program as simple as possible (ie. so that you are testing what you *think* you are testing!), you should also get into the habit of using more descriptive variable declarations, such as 'int1', 'int8', 'int16', 'int32', etc., etc. This really helps when looking at your code!
John |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Wed Jun 25, 2014 12:14 pm |
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ezflyer gave you an an excellent detailed answer.
but what is your real QUESTION HERE?? |
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jocaropi
Joined: 25 Jun 2014
Posts: 18
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| Posted: Wed Jun 25, 2014 12:17 pm |
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| It's "solved", I was mistaken with the calculations of how much time would it take the PIC to execute the code. |
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