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I\O Speed Problem

Siddharth Vaidya

Hi,

I am using my LPC2364 at 75Mhz and i am getting maximum i|O frequency upto 13MHz only. Even if i toggle just one bit.

I want upto 16MHz minimum frequency of I\O. Can i do it with Thumb instructions or 13Mhz is the max??

Parents
  • 0 in reply to Siddharth Vaidya

    The ideal speed of 18MHz will be for something like this

    LDR R0,=FIO2PIN0
    MOV R1,#0x01
    MOV R2,#0x02

    STRB R1,[R0]
    STRB R2,[R0]
    STRB R1,[R0]
    STRB R2,[R0]
    ....

    ANY data loading instructions in between the STRB will reduce the speed (say a mov instruction - 1 cycle which will be required in your case) will reduce the speed.

    If your requirement is only that a limited sequence output should be fast, then you can hold the data in registers (say R1-R10)and store it to the IO in succession.

    Suvidh

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  • 0 in reply to Siddharth Vaidya

    The ideal speed of 18MHz will be for something like this

    LDR R0,=FIO2PIN0
    MOV R1,#0x01
    MOV R2,#0x02

    STRB R1,[R0]
    STRB R2,[R0]
    STRB R1,[R0]
    STRB R2,[R0]
    ....

    ANY data loading instructions in between the STRB will reduce the speed (say a mov instruction - 1 cycle which will be required in your case) will reduce the speed.

    If your requirement is only that a limited sequence output should be fast, then you can hold the data in registers (say R1-R10)and store it to the IO in succession.

    Suvidh

Children
  • 0 in reply to Suvidh Kankariya

    Hi Suvidh,

    Thank you for the explanation. I have to increment the same from 0 to 1024(decimal). and i can not have that many registers. Even if i use the increment then it will waste one cyle.

    I have got a way for it. i am using counters for the same. i am using commands

    FIOPINSET=0x01;
    FIOPINCLR=0x01;

    this usis the same method that u have written. 0x01 is stored in a register and it gives me 18MHz pulses. I am generating the rest from giving this signal to a counter.

    Thank you for the replies.