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Why divide the clock by two in 8086 microprocessors?

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vedaprabhu

vedaprabhu

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Why divide the clock by two in 8086 microprocessors? and also why divide by 12 in 8051?
 

To obtain 50% duty cycle clock. If there is a PLL circuit into chip (for example am188es, elan sc520), it is no need to divide by two.
 

I'm not sure if this is correct.
I remember the recomended clock duty cycle of the 8086 is 33%. The clock signal is obtained by a divide by 3 circuit. The 8284 is a clock circuit often used for clock generation with 33% duty cycle, with 8086.
 

lol

you divide the clock by two becouse it is double banked

wake up
 

I made a mistake :cry:, 8086 requires a 33% duty cycle clock.
 

vedaprabhu said:
Why divide the clock by two in 8086 microprocessors? and also why divide by 12 in 8051?
Click to expand...

The internal workings of the ‘85 require clock with a 50% duty cycle, and division by 2 ensures that the clock signal has exactly 50% duty cycle (internally it is nonoverlapping two phase) ..
 

thank you all! I got my doubt cleared..
 

AA,
I guess all answers are wrong. In 8086, there are 2 clocks per machine cycle. So when you divide clock cycles by 2, you get the number of machine cycles needed. In 8051, there are 12 clock cycles per machine cycle. So when you divide clock cycles by 12, you get the number of machine cycles needed.
BR,
Amr Ali.
 

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