how to use a Internal Rom of 8051 microntroller

[tigerraj]

As we know 8051 has 4Kb of flash memory and 128 bytes of RAM.
Now I want to design a very simple digital clock which will show the time.
For this we will just inttialize the timers to invoke at a desigered unit of time and show the particular value of time in some output device.
now if we remove the power supply and connect it again then the recent time will be cleared to default value.

For this sort of problem cann't we utilize the remaining 4kb of memory to hold these changing variable so that we could initialize the timer from this value when we reset the system.

 

[FvM]

No you can't. You need a backup battery.

 

[bobsanjose]

Depends on your specific 51 derivative. Some are built from EEPROM cells and you could save the last known time when you power off, IF your systems knows ahead of time when that happens (power fail with large C)
You will not be able to track time, but you might be able to track usage of your device. Time will fly by while the device is switched off, usage is "0" during off mode.

hth, Bob
as FvM mentioned a backup battery and a Real-Time-Clock would make life a lot easier though.

 

[IanP]

Not only one needs a battery, but an IC that will count (and remember) the time regardless whether external power is present or not ..
You can select RTCs (real-time-clock) with built-in battery ( DS12877) or with 3V lithium battery support ( DS1302 – DS1307 ) ..
Your call ..

Rgds,
IanP

 

[tigerraj]

Thanks to all who replied me
But I think You People didn't understand my question.
DS1307 is the easiest way for timing, through Battery backup we can run the system running at least in sleep mode .

timing was only one example for my queries. Actually i want to store the data into the onchip ROM of 8051 while it is running mode.

This will be the good example of this question than timer.
I want to design the visitor counter which will count the no. of visitor and when it reach 1000 it have to alarm or something other indication.
Now at the state when count was 999 power system fails or system get reset that may be any cause. Then when system starts count will begin from 0.

That's why i want to store this variable "count "into the onchip ROM of 8051 so that we can retrive the count during the next startup.
Is it possible to update the ROM of 8051 during run time

 

[IanP]

ROM = READ ONLY memory ..


You need external memory, EEProm or NV SRAM ..
**broken link removed**

Rgds,
IanP

 

[tigerraj]

But 8051 also have flash ROM ? what do u think about this

 

[IanP]

Unfortunatelly, while running, you can not "touch" the FLASH memory ..
What you can do though, in, for example, the AT89S8253 there is 2k of EEPROM data memory that can be easily utilized for your purpose .. see:
http://www.atmel.com/dyn/resources/prod_documents/doc3286.pdf

Rgds,
IanP

 

[tigerraj]

Great Thanks for suggestion

Added after 6 minutes:

now is there any guidence/help source to use this memory

 

[IanP]

AT89S8253 Primer

http://www.atmel-grenoble.com/dyn/resources/prod_documents/doc3655.pdf

Rgds,
IanP

 

[dinesh401]

As we know 8051 has 4Kb of flash memory and 128 bytes of RAM.
Now I want to design a very simple digital clock which will show the time.
For this we will just inttialize the timers to invoke at a desigered unit of time and show the particular value of time in some output device.
now if we remove the power supply and connect it again then the recent time will be cleared to default value.

For this sort of problem cann't we utilize the remaining 4kb of memory to hold these changing variable so that we could initialize the timer from this value when we reset the system.

haai.....the link below will helps u
https://what-when-how.com/8051-microcontroller/accessing-code-rom-space-in-8051-c/

Go below and see how to access a code memory in 8051.