8051 Micro controller
Upon reset all port pins and port registers are high. I follow these instructions...
P0=0x00; P0=0xFF;
Now ,the result is - All P0 registers are high & all P0 pins are low.
Q1) Does this low P0 pins indicate high impedance floating load in the case of P0?
Now, I start the program with the following instruction only.
P0=0xFF;
But All P0 registers and pins remain high.
Q2)What is the difference here? What's happening inside circuitry in both cases?
What part of the 8051 documentation are you stuck with?
In the old days, the key documentation set was commonly known as the "bible" for the 8051.
It is getting harder to find these - there should be a clue in that - but here are some archived copies:
Chapter 1 - 80C51 Family Architecture: ecee.colorado.edu/.../p8051arc.pdf community.nxp.com/.../DOC-334648
Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: http://www.keil.com/dd/docs/datashts/philips/p51_pg.pdf ecee.colorado.edu/.../p8051pg.pdf community.nxp.com/.../DOC-334650
Chapter 3 - 80C51 Family Hardware Description: courses.cs.washington.edu/.../famhdwr.pdf community.nxp.com/.../DOC-334649
Keil still list some books: http://www.keil.com/books/8051books.asp
And, of course, you should be studying the manufacturer's documentation for the particular part(s) you are using.
But you should really be asking yourself whether the 8051 is an appropriate place to be starting in this day and age ...
if you are using one of the older derivatives that fully adhere to the original standard P0 dces not have "weak pull-up" as P1, p2 & p3
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