Forum: ARM programming with GCC/GNU tools ARM7 tdmi clock problem aduc7026

von Zdenek Krejci (Guest)

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Hi to all
Im having problem to get clock working... Im trying to get run the core 
on 41.78MHz to be able to make a delays of 70 nS. If Im right than it 
should work 1/ 41.78 = 23nS so even if one instruction would take two or 
three clock cycles.
The system configuration is 32 Khz external crystal->PLL-> 41.78 MHz
But when I try to set everything it still seems to run on factory 
default 5.22Mhz.. My code is
(in main)
PLLCON = 0x21;// User value set 32 kHz Input & PLL
PLLKEY2 = 0x55;

POWKEY1 = 0x01;
POWCON = 0x00;//User value set Active mode & clock divider 0
POWKEY2 = 0xF4; 

GP4DAT ^= 0x00FF0000;// Just to see LED
sysDelay_ms(1000);//My delay function where just simple while's are implemented

von Zdenek Krejci (Guest)

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Hi thanks for your reply I just havent time to have look. Now I was 
trying the links but the are not working or just not for me?

von Martin T. (mthomas) (Moderator)

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@Zdenek Krejci
Retry with just the POWKEY, POWCON, POWKEY sequence without the PLLKEY, 
PLLCON. This should do when using the internal 32kHz R/C as source for 
the PLL. Anyway: the question can not be answered without showing more 
code, at least the implementation of sysdelay_ms().

@"jenny Lau"
There is no need to place links to Chip-Broker websites here. They will 
not help to solve the OP's issue. The only useful technical information 
on the linked pages have been links to datasheets which can be 
downloaded from the ADI website directly.

von Zdenek Krejci (Guest)

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Ye I was trying that now without the PLLKEY but no luck... I was now 
trying to make sure different way, to initalize ADC to see how many 
samples I get when connect 100Khz on its input... If Im right, if the 
core runs corectlyu on 41Mhz than the ADC should be able to make 1MSPS 
so I should have about 10 samples on period... BUT Im getting only about 
4 samples on these 100Khz...
So either the clock is still not switching on 41Mhz or im doing 
something wrong with the ADC... Well anyway this info from datasheet is 
weird.. Table 15. ADCCON
fADC/1. This divider is provided to obtain
1 MSPS ADC with an external clock <41.78 MHz.
Does it mean that the ADC will not run on 1MSPS when the core have those 
41MHz from PLL? It just must be external??

von Zdenek Krejci (Guest)

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Ye forgot here is the code
void adc_init(void){
/*ADC power control: power up as there is at least 5us before corect conversion*/
ADCCON |= (1<<5);  
/*.....................ADCCON Resgister*/
/*Clock speed:fADC/1 1 MSPS with ext osc 41,78Mhz*/
ADCCON &= ~(1<<12);
ADCCON &= ~(1<<11);
ADCCON &= ~(1<<10);
/*Acquisition time*/
ADCCON &= ~(1<<9);
ADCCON &= ~(1<<8);
ADCCON &=~(1<<6);
/*Conversion mode: single ended*/
ADCCON &=~(1<<4);
ADCCON &=~(1<<3);
/*Conversion type: Continuous soft conversion*/
ADCCON |=(1<<2);
ADCCON &=~(1<<1);
ADCCON &=~(1<<0);
 // Enable start conversion
  ADCCON |= (1<<7);
/*.....................REFCON Resgister*/
/*Reference sellection:*/
/*For internal*/
REFCON |= 1<<0;/*Select internal*/


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