Questions tagged [8051]

The "8051" is a (still) very popular chip in the Intel MCS-51 micro controller series.

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problem with sd card video door phone

I'm working on the code of a video door phone and I'm trying to improve it. with 16 GB SD card the pictures that the camera takes can be seen on the LCD but when I connect the SD card to PC using a SD ...
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How do I enable the divided clock output on an AT89LP51RC2?

When using External Clock Source A on an AT89LP51RC2, the datasheet says: XTAL2A may be left unconnected, used as general purpose I/O P4.7, or configured to output a divided version of the system ...
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Why we used 128 bytes internal RAM memory instead of 256 bytes in 8051?

... since using 7-bit in 8-bit address bus wastes one wire. In 8051 there is a 8-bit address bus for internal RAM out of which we just use 7 wires making it addressable to just 128 byte locations, why ...
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How decode serial data stream

I am trying to decode a data stream. This signal comes out of an STC 8H1K16 micro-controller. It is from the pin labeled TxD is the picture. When I trigger the signal I am trying to understand I get ...
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8051 seven segment 1-9, and reset to 0

This is a university assignment, last part of 3. I cannot find any useful notes describing looping in the 8051 assembly language in the course resources, and the lecturer isn't replying to questions. ...
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practical connection of LED to a MCU

While aiming to blink an led with this 8051 MCU, I used configuration 1 to connect my LED. It doesn't work. But 2 and 3 worked. logically, there should not be any reason behind why configuration 1 do ...
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8051 interrupt within interrupt high vs low priority

I am learning and experimenting on the 8051 (AT89C51). From what I have learnt so far regarding interrupts, I understand that an interrupt with a higher priority can interrupt an interrupt with a ...
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8051 AT89C51 PSEN ALE pins, not to be used

I am new to microcontroller programming, and am about to lay hands on the 8051 AT89C51. I want to do some basic things like flashing LEDs, microcontroller to microcontroller data exchange etc. I have ...
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timer mode 1 and edsim giving different result

IN 8051, Timer 0 in mode 1, if the maximum count reaches, the timer should displayed with 0000H, and should stay 0000h until we stop it and start again . But with this program ...
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8051 baud rate and timer connection

I was learning serial communication of 8051, in datasheet I have found this: it looks like both of the SBUF transmitter and SBUF receiver are parallel in serial out and serial in parallel out shift ...
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Max232 to DB9 connection confusion

The picture shows standard connection between 8051 and DB-9 via MAX232. 14th pin is the translated output of the transmitted data by 8051, so this should be connected to the receiver pin of DB-9, ...
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Frequency counting program - Timers in 8051

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A question on timers in 8051

Suppose the timer 1 of 8051 has finished counting, and raised TF1. Since it rolls back to 0, so currently TH1=00,TL1=00, and assume the bit TR1 is still set. At this moment, if we just clear the TF1 ...
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8051 timer delay calculation

In the following program MOV TMOD, #01H HERE: MOV TLO, #0F2H MOV THO, #0FFH CPL P1.2 ACALL DELAY SJMP HERE DELAY:SETB TR0 AGAIN: JB TF0,AGAIN CLR TF0 CLR TR0 RET ...
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Making a port as input in 8051

As we all know in order to make a port input in 8051 we have to write FFH to that. That is, MOV P1, #0FFH after this execution does it mean all the pins of the ...
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hex value is treated as decimal value

This is from Mazidi's book on microcontroller. As we can see we are aiming to add these two values 17H and 28H in HEX and want to get their sum in BCD, definitely their sum is 3F and which should be ...
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MCS-51 addressing memory with DPTR needs ACC

So as I have learnt the DPTR is used to store all of the 64k addresses of ROM space and RAM (according to our demand) so that we can use register indirect addressing through this 16 bit DPTR. Suppose ...
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8051 (AT89S51) on power on pin P3.0 output goes high for a brief moment

This is my first microcontroller project. Goal is to keep relay on for specified amount of time with pause and resume feature. I am using ports as follows: P1 to drive LCD 16x2 display. P0 and P2 to ...
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8051 DPTR and program counter difference

So as we know both of the program counter and DPTR are 16bits in 8051 and hence both of them are capable of reaching 216 possible locations, which is sufficient for both RAM and ROM, then why DPTR is ...
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Registers in 8051 microcontroller

Recently I was reading about 8051 microcontroller instructions, and come to know that it has a set of registers from \$R_0 - R_7\$.Later on, when I was introduced with register banks then I feel like ...
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4-bit mode of LCD-1602 using 8052 µc

I try writing "NO" in the LCD using 4-bit mode. So, I programmed the AT89S52 to send the upper nibble first to the last 4 data inputs of the LCD. I used AND operation to eliminate the lower ...
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Finding maximum sink and source currents from datasheet

How can I find the maximum sinking and sourcing currents of different pins in a microcontroller (namely 8051) from its datasheet? Edit: I have downloaded and looked at the datasheet, I just can't read ...
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How does the OV(Overflow flag) of the 8051 work and how does it differentiate between signed and unsigned digits?

If a number is 8 bit, the maximum value it can have is 2^8 or (1111 1111). In the OV flag, the last digit or the MSB decides the sign, but how does the overflow flag know if it is the "signed MSB&...
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What is the difference between Register Addressing mode and Direct Addressing mode(8051)?

I find that there is no difference between the Register Addressing mode and the Direct Addressing mode. Can anyone tell the difference with respect to the 8051 microcontroller ?
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8051 / EFM8LB1 / programming via C2 after PCON0.STOP := 1?

Yesterday I wanted to see, how much power my EFM8LB1 uses, when it has just this firmware with bootloader disabled: ...
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Understanding oscillation frequency for SAF-C509 processor

Good day. For the time being, I'm reversing automotive ECU which has Intel51 architecture processor - SAF-C509 by Infineon/Simens. Its command exection part has 6 states with 2 phases for each state. ...
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Encryption library for an 8051 microcontroller

I've programmed an 8051 microcontroller to send data out through an external transmitter (just a few bytes per transmission). I'm looking to encrypt this data in my microcontroller's program. I have a ...
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problem in programming ISR in 8051

in this code : ...
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Need more than two external interrupts in 8051

I am working with 8 YS-17 flame sensors and may need more in the future. There are only two INT0 and INT1 in port 3. Is there any way to get the other interrupts or I/Os to work as external ...
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Is anyone familiar with EDsim? [closed]

I'm learning the basics of the microcontroller 8051 and I wrote a program that requires me to toggle a button situated in the ADC of the chip . Since I don't have the board , I worked on a software ...
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firmware testing methods

This is my first question here from the community :) So I have inherited some bad embedded code, the whole firmware is a messy spaghetti state-machine that has an infinite number of states! and it is ...
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How to use mode 0 in 8051?

I tried to use timer0 in mode 0 of AT89S52 for blinking a led for 1 second using this code: ...
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.c to .hex file conversion without using any IDE

I am new to microcontroller programming. I have a program written in C or assembly language which I need to convert into a .HEX file to flash into the 8051 microcontroller. I do not want to use an IDE ...
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8051 initializing data in external memory

I am trying to understand the use of external memory with an 8051. When you are using external memory with something like C8051F962 where you have to configure the ports to access the memory, how do ...
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Why 8051 microcontroller uses four different ports for I/O instead of using address bus and control signals

8051 has four ports for I/O .Therefore four peripherals can be connected to it at a time . My question is why doesn't it use the address bus to activate a specific peripheral ...and then use the data ...
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Cloning a 8051 flash with an Arduino

I have a 8051 microcontroller and want to copy the flash memory. I have an Arduino, a cp2102 usb to UART module and an 8051 microcontroller. The 8051 is a zen3309AD. How do I achieve this task. I ...
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What is the difference between ram and registers in 8051 vs arm v7?

Recently i am confused between the difference between ram and cpu registers.I have studied 8051 arch. and in that we had addressing for cpu registers in ram level (e.g. the adddress for R0 register in ...
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8051 to I2C backpack/4 bit LCD Byte Construct Probelms

Been feverishly writing bit bang code in assembly for this I2C backpack/4 bit LCD and dont quite understand the binary constructs I need to display text. Im trying to learn this the real way, not the ...
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What is a page in 8051 microprocessor?

https://www.hobbyprojects.com/8051_tutorial/acall_absolute_call.html I was learning about acall on the above website, but then came across the term page. What exactly is a page?
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8051 microcontroller assembly language elevator coding

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How these timer values are derived?

I have a 8051 micro controller ,it has timer0,1,2,3 with different modes. in timer0,mode0, i got a sample code (as shown below). datasheet 8051 from that code ...
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In asynchronous communication how is the frequency same but clocks of both devices different?

Am currently studying 8051 microcontroller and in the course the lecturer told that in communication the frequencies of sender and receiver should be same else they will get different bits of data at ...
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1 vote
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What happens at hardware level when we feed a code? [duplicate]

I wanted to know what hardware is installed in 8051 such that whenever i write a program it accepts it and execute it. My query is what happens at the hardware level whenever i feed a program to 8051.
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Two switches and two LEDs using 8051

I am trying to work around a circuit and my requirement is as follows: - There are two inputs and two outputs. Each input controls an individual led. I am writing a code for this requirement using a ...
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minimizing waiting time for 8051 port state

I made myself a project with standard 8051 microcontrollers (AT89S52 and AT89C4051) and will be making more with the same due to price and availability. When data is being sent from one GPIO pin from ...
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ENC28j60 ethernet interfacing with efm8lb1 help needed

I am a newbie to ethernet controller. I went through ENC28j60 documentation But I couldn't find a proper example similar to my project. EFM8LB1 will read some sensor data (for example sensor data '...
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How can I code in a buzzer while using a 7-segment in an 8051

I'm currently working on a small queuing system where whenever someone presses a button (which I have linked to INT0), my 8051 would increase the register and would display a higher number on the dual ...
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Why does this driver not have a load resistor?

Im trying to drive a motor with this kind of circuit since my micro is an old 8051. The voltage I use is 5V and PowerV is also 5V. I also have a 56 ohm 1/2 watt resistor in series with my motor ...
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Weird error pattern on CC2541, the 8051 core

I am playing with the debug interface on the TI CC2541. It seems to be working fine, seeing correct chip ID etc. The interface has a DEBUG_INSTR command that lets you submit and execute an ...
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Grounding GPIO pins during 8051 programming

I'm trying to make a programmer for the 8051 microcontroller IC's, specifically the AT89C2051. I saw a circuit online (the blowit programmer) in which the unused GPIO pins are left floating. When the ...
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