Doubt Microcontroller Memory

[electronicslearner77]

Hi all,

Generally I have seen that all the microcontrollers provide internal flash memory, internal RAM and other memories. I wanted to know does this internal memory depend on the address lines of the microcontroller? Also what are the factors on which the manufacturer decides these internal memory sizes?

Please someonoe help me to understand this.

thanks in advance,
Satya

 

[Ian Rogers]

All micro's provide a selection of different combinations..

Some micro's don't provide much memory... Some do.

Take the PIC for example...
You can get 1k, 2k, 4k, 8k, 16k etc.. flash memory... This increases the cost of the component.
Then there is a certain amount of SRAM which also increases the size of the device cost.
Lastly we get EEprom. many devices have a few bytes available, again down to costs.

You select what chip you need... A consumer would select the most practical device to suit their needs..

Chip manufacturers are constantly looking at the market, to see what's being used, trying to fill that need..

So ultimately.. We decide memory sizes and device functionality..

 

[WTP Pepper]

Some like the 8051 core have dedicated instructions as to what memory you wish to use and some are more cumbersome.

MovA, 0x20 will put into A what's held in internal memory(RAM) at 0x20


Mov DPTR, #0x20
movx A,@DPTR will read external memory from the same memory location but from a physical different place. External memory.

clr A
Mov DPTR, #0x20
movc A,@(DPTR+A) will read memory from the same memory location but from a physical different place. Code memory

 

[ronsimpson]

Generally I have seen that all the microcontrollers provide internal flash memory, internal RAM and other memories. I wanted to know does this internal memory depend on the address lines of the microcontroller? Also what are the factors on which the manufacturer decides these internal memory sizes?
Satya

Address lines (internal and external) come in common numbers. Many have 16 address lines for addressing 64k of memory. They probably do not use all the lines. I just opened a PIC data sheets and it has 12 address lines for a maximum of 4k instructions. That part comes in 0.5k, 1k , 2k and 4k of memory. The CPU is very complex and they do not want to change it. Memory is added on. One part I know too well; the CPU has 16 address lines and the flash memory came in 4k blocks, where you can get 1, 2, or 4 of the memory blocks on the die.