PUSH & POP
STACK:
it s part of RAM in which data will store temporary during execution of program.
STACK work on last in first out principal.to store and retrieve data during program execution in stack push and pop instruction work for it.
PUSH:
its used to store data into stack.
POP:
to retrieve data from stack.
SP:
stack pointer is 8 bit register which store value of top of the stack.
by default stack pointer contain 07h.
PUSH...
Wednesday, September 11, 2013
10:30 PM
1 comment
In 8051 micro controller have in built RAM and ROM,but size of this memory is limited size of RAM is 128 byte while size of ROM is 4KB some time we need more memory then this so we connect external memory with micro controller.
access external RAM
To access external RAM we used MOVX instruction.
MOVX A,@DPTR;this code used for read data from external RAM.
MOVX @DPTR,A;this code used for write data into external RAM.
access External...
Wednesday, September 4, 2013
12:16 AM
3 comments
Serial Interface
The serial port of 8051 is full duplex, i.e., it can transmit and receive simultaneously.
The register SBUF is used to hold the data. The
special function register SBUF is physically two registers.
One is,
write-only and is used to hold data to be transmitted out of the 8051
via TXD.
The other is, read-only and holds the received data from
external sources via RXD. Both...
12:16 AM
1 comment
In this mode PCON (power control register).in this register two bit play important role for power control of 8051.
Below show the format of PCON
8051 has two power saving modes.they are
idle mode
power down mode.
The two power saving modes are entered by setting two bits IDL and PD in the special function register (PCON) respectively.
POWER DOWN MODE:
the schematic diagram of power down mode shown below.
By setting the PD bit of...
Tuesday, September 3, 2013
11:28 PM
2 comments
To write data to serial port
To write a byte to the serial port one must simply write the value to the SBUF
(99h) SFR.
if you wanted to send the letter "A" to the serial port, it
could be accomplished as easily as
MOV SBUF,#A
Upon execution of the above instruction the 8051 will begin transmitting...
Tuesday, July 9, 2013
11:35 PM
No comments
Interrupt
There are five interrupt sources for the 8051, which means that they
can recognize 5 different events that can interrupt regular program
execution.
there are five interrupts :,TF0,(INTR1)',TF1,RI/TI
Each interrupt can be enabled or disabled by setting bits of
the IE register. Likewise, the whole interrupt system can be disabled by
clearing the EA bit of the same register. .
Now, it is necessary to explain a few details referring...
11:08 PM
No comments
TIMING
If a counter is programmed to be a
timer, it will count the internal clock frequency of the 8051 oscillator
divided by 12d.
As an example, if the crystal frequency is 6.0
megahertz, then the timer clock will have a frequency of 500 kilohertz.
The
resultant timer clock is gated to the timer by means of the circuit
shown in Figure.
In order for oscillator clock pulses to reach the
timer, the C/(T)' bit...
Monday, July 8, 2013
11:55 PM
49 comments
Counters and Timers
Many
microcontroller applications require the counting of external events,
such as the frequency of a pulse train, or the generation of precise
internal time delays between computer actions. Both of these tasks can
be accomplished using software techniques, but software loops for
counting or timing keep the processor occupied so that other, perhaps
more important, functions are not done. To relieve the processor...
1:50 AM
No comments
Branch Instructions
There are two kinds of branch instructions:
Unconditional jump instructions: upon their execution a jump to a new
location from where the program continues execution is executed.
Conditional jump instructions: a jump to a new program location is
executed only if a specified condition is met. Otherwise, the program
normally proceeds with the next instruction.
ACALL addr11 - Absolute subroutine call
addr11:...
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