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???
08/10/06 12:15
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 		 #121955 - did you not read
Responding to: ???'s previous message
Refering to 89LPC9xx usermanual, the clock used for timer is PCLK which is 7.xxMhz/2 (CCLK/2). Hence, i thought the timer reload value should be calculated this way:

(65535-x)(1/3.xxM) = 1/3.xxM
=> x = 65534
=> TH0 = 0xff, TL0 = 0xfe

I think the above formula is incorrect since the output doesn't create a clock pulse of 3.xxMhz/2.

did you not read
there is no way you can do that.
entering an ISR usually takes 4 cycles (maybe in the LPC only 2 - look it up) and the return takes - again look it up - cycles. Thus it is patently impossible to create anything 1/2 oscillator by using an interrupt.

it's bible time

as jan suggetsted get familiar with mode 2.

Erik

List of 31 messages in thread
TopicAuthorDate
FAQ: P89LPC9221            01/01/70 00:00      
   Code Architect            01/01/70 00:00      
   that\'s impossible            01/01/70 00:00      
      pin toggle            01/01/70 00:00      
         Sure, but that does not achieve 3.xx MHz            01/01/70 00:00      
            interrupt            01/01/70 00:00      
               that will not do it as I did show in my post            01/01/70 00:00      
                  mode 2            01/01/70 00:00      
                     slovakian math ?            01/01/70 00:00      
                  usermanual of 89LPC9xx insufficient            01/01/70 00:00      
                     please read the WHOLE thread            01/01/70 00:00      
                        Can timer mode 2 overcome interrupt overhead?            01/01/70 00:00      
                           with mode 2 the reload is automatic as \"the            01/01/70 00:00      
                     did you not read            01/01/70 00:00      
   Re: 50kHz output...            01/01/70 00:00      
   I eneterd a FAQ on this            01/01/70 00:00      
      Where? I can't see it            01/01/70 00:00      
         here            01/01/70 00:00      
            I think you misplaced it...            01/01/70 00:00      
               I placed the FAQ correctly but - shame on me - pl            01/01/70 00:00      
                  What is the fastest frequency of Timer Mode 2            01/01/70 00:00      
                     fastest output            01/01/70 00:00      
                        Couldn't Wait in Endless Loop            01/01/70 00:00      
                           NOOOOOOOOO            01/01/70 00:00      
                              Where should i CPL p0.5 then?            01/01/70 00:00      
                                 oooh, then it's impossible, of course            01/01/70 00:00      
                                    89LPC9221 i2c interface            01/01/70 00:00      
                                       I am against "sharing code" but it is there            01/01/70 00:00      
                                          I2C interface with 89LPC9221            01/01/70 00:00      
                                             what does CodeArchitect do ?            01/01/70 00:00      
                                             push-pull?            01/01/70 00:00      

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