Extra RAM and SRAM for PIC16,18F series

[sairfan1]

Hi,

Im looking for some cheap solution to add 1KB to 5KB RAM to use in 8bit PIC projects. Im also looking for some solution for storage from 1MB to 10MB memory.

Please share your experience. Thanks.

 

[doraemon]

Hello!

For small micro controllers, it's difficult for 2 reasons:
- There is no EMIF interface
- If you do it, you will eat all the available pins (in the unlikely case that there are enough)
to drive the memory.

One solution I am using is SPI SRAM. Microchip makes cheap 8-pin SPI SRAMS. It's not as
fast as the CPU memory because you have to access it by SPI, but it might be a good way
to do what you want, and you can have 128 kBytes. And these chips are reasonably small.

As for storage, you mean permanent storage? There are flash chips, about same size,
that can hold 32 Mbytes.

Dora.

 

[shell.albert]

Yeath.
As mentioned above,it does not has a external memory interface in low grade 8-bit micro-controller usually.
And the amount of pins is not enough for connecting parallel RAM chips with PICs.
The only way to solve your problem is to choose a serial communication interface IC,such as I2C,SPI,.etc.
This is my recommend.

 

[sairfan1]

One solution I am using is SPI SRAM.

you got me correct I'm looking for same solutions what you advise, now a days working with Graphic LCDs we need more RAM and Flash memory,
Which type of memory you recommend for storage? Flash is good for long term and speed for reading and writing?

 

[doraemon]

Hello!

you got me correct I'm looking for same solutions what you advise, now a days working with Graphic LCDs we need more RAM and Flash memory,
Which type of memory you recommend for storage? Flash is good for long term and speed for reading and writing?

I cannot reply. Flash can be a solution, but it depends on the processor you are using because
you cannot access one byte at at time, but one page (i.e. if you want to read the last byte of a page,
you have to read the whole page). I did a trick many years ago to allow to read a single byte, but
anyway in this case you have to clock out dummy bytes until you get the byte you want, so you loose
a lot of time clocking (on the average 128 times more than a memory that can be accessed by byte).

And since I don't know at all what you want to do, I cannot choose for you.

Dora

 

[paulfjujo]

hello,

you have to considere about the speed.
Eeprom like 24LC256 32Kbytes are very slow if you want to write byte per bytye
>5mS ,or if you can use intermediate storing in Ram for one page size of
64 bytes,you can write page per page at 130uS per page.

see also FRAM for speeder devices.