ROM & RAM inside pic - Electronic Circuits Projects Diagrams Free

kimsiang85 · 28th March 2008, 02:04 PM

i am using pic16f877a for my final year project.
i have written some coding for the microcontroller and it used around 22% of RAM and 76% of ROM.

why the usage of the RAM and ROM have such large difference??
can i use the capacity of RAM and ROM till maximum?
will it slow down the performance of PIC or spoil the PIC??
do pic16f877a have the limit like for example just can use till 90% of RAM and ROM

so, i hope you all can give me some advice regarding on this.
thanks

blueroomelectronics · 28th March 2008, 02:27 PM

You can use 100% of RAM, FLASH (ROM) and EEPROM on any PIC.

Pommie · 28th March 2008, 02:30 PM

You must have a lot of code to fill 76% of a 877. If you post your code we can probably suggest ways to make it more compact.

Mike.

NightFalcon90909 · 28th March 2008, 05:24 PM

On a PIC, ROM is the memory that holds the code. RAM holds data collected from the environment that the robot collects and holds. I must say I am astonished that you are filling so much of your memory up with an 877... I would definitely like to see... I would be very surprised if it couldn't be trimmed a bit

donniedj · 29th March 2008, 03:21 AM

kimsiang85:
You should know that a microcontroller is not a serial access device like a cassette tape. You can easily fill the entire code space by placing all your code at the end of ROM and filling the upper locations with 0's, F's and such. Just because code is at the end of address space does not make it slow because it can be accessed is the same time as the very first byte of code, a.k.a. random access.

What impacts the PIC speed is the techniques of excessively using macros, calling tables, and moving bulks of RAM using hard coded labels as opposed to indirect addressing, and placing faith in compilers.

kimsiang85 · 3rd April 2008, 01:56 PM

sorry for late reply.
i am rushing for my final year project and tomorrow i need to go out for presentation.
back to the topic
there are many redundant coding for my code.
i have reduce many of them and now i get 20-30% for rom and ram
thanks for all your advice

Pommie · 3rd April 2008, 01:59 PM

Quote:

Originally Posted by kimsiang85

i am rushing for my final year project and tomorrow i need to go out for presentation.

Good luck, hope everything goes well.

Mike.

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28th March 2008, 02:04 PM	(permalink)
kimsiang85	ROM & RAM inside pic i am using pic16f877a for my final year project. i have written some coding for the microcontroller and it used around 22% of RAM and 76% of ROM. why the usage of the RAM and ROM have such large difference?? can i use the capacity of RAM and ROM till maximum? will it slow down the performance of PIC or spoil the PIC?? do pic16f877a have the limit like for example just can use till 90% of RAM and ROM so, i hope you all can give me some advice regarding on this. thanks

28th March 2008, 02:27 PM	(permalink)
blueroomelectronics	You can use 100% of RAM, FLASH (ROM) and EEPROM on any PIC. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

28th March 2008, 02:30 PM	(permalink)
Pommie	You must have a lot of code to fill 76% of a 877. If you post your code we can probably suggest ways to make it more compact. Mike.

28th March 2008, 05:24 PM	(permalink)
NightFalcon90909	On a PIC, ROM is the memory that holds the code. RAM holds data collected from the environment that the robot collects and holds. I must say I am astonished that you are filling so much of your memory up with an 877... I would definitely like to see... I would be very surprised if it couldn't be trimmed a bit __________________ If it is broken, let's fix it. If it is working, let's make it better.

29th March 2008, 03:21 AM	(permalink)
donniedj	kimsiang85: You should know that a microcontroller is not a serial access device like a cassette tape. You can easily fill the entire code space by placing all your code at the end of ROM and filling the upper locations with 0's, F's and such. Just because code is at the end of address space does not make it slow because it can be accessed is the same time as the very first byte of code, a.k.a. random access. What impacts the PIC speed is the techniques of excessively using macros, calling tables, and moving bulks of RAM using hard coded labels as opposed to indirect addressing, and placing faith in compilers. Last edited by donniedj; 30th March 2008 at 05:13 PM.

3rd April 2008, 01:56 PM	(permalink)
kimsiang85	rom and ram sorry for late reply. i am rushing for my final year project and tomorrow i need to go out for presentation. back to the topic there are many redundant coding for my code. i have reduce many of them and now i get 20-30% for rom and ram thanks for all your advice