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Could any one help me, How to calculate the reg. value to achieve a desired delay in 8051 micro controller. Suppose I need 250ms delay .What should be the reg. value ,I have to take.
For HERE loop, we have (4x250)x1.085μs=1085μs. For AGAIN loop repeats HERE loop 200 times, so we have 200x1085μs=217000μs. But “MOV R3,#250” and “DJNZ R2,AGAIN” at the start and end of the AGAIN loop add (3x200x1.805)=651μs. As a result we have 217000+651=217651μs.
from the The 8051 Microcontroller and Embedded Systems Using Assembly and C-2nd-ed
Very helpful for me
I should also add that was assuming one machine cycle lasts 12 oscillator periods like the AT89C51 and also using a 11.0592 MHz crystal
11.0592/12 = 921.6 kHz;
machine cycle is 1/921.6 kHz = 1.085μs
If a memory chip of size 256 kilobytes (256 x 1024 x 8 bits),
how many wires does the address bus need, in order to be able to specify an address in
this memory?
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