Mid-capacity RAM with serial connection to MCU?

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I'm looking for a mid-capacity static RAM part that I can use with a TI
MSP430 series MCU using a few interface lines and serial transfers. I
am finding a few serial-interface static RAMs (such as the Philips
part) but those I'm finding are very small capacity for my application
- 256 bytes or less. I need something in the 2 to 8K byte range, but
static RAMs in that range are parallel (address/data) interface which
would create the need for a bunch of support circuitry I'd like to
avoid. Any suggestions of where to look? Very tks.


Re: Mid-capacity RAM with serial connection to MCU?
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I have also been looking for this type of thing, but I cant find
anything.
The only option I see is to use another small CPU and progrsam it to
act like a serial RAM chip.

-howy


Re: Mid-capacity RAM with serial connection to MCU?
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You might consider FRAM from Ramtron: 4k, 16k, 64k or 256k serial devices
available. Access speeds are good, reasonable range of voltages supported
(2V7 ... 5V5) depending on part.

    Andrew



Re: Mid-capacity RAM with serial connection to MCU?
snipped-for-privacy@hotmail.com says...
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I've had good results with the 32kx8 SPI serial FRAM chips from
RamTron.   You get the added bonus that the data in the chip
is non-volatile.  The SPI versions will run as fast as the SPI
bus on the MSP-430.    Like other serial RAMs that  require sending
an address and command before reading and writing data, you get
much better performance reading and writing blocks as opposed to
random bytes.

http://www.ramtron.com/doc/Products/serial.asp


Mark Borgerson


Re: Mid-capacity RAM with serial connection to MCU?
Thanks very much for the pointers - I just looked at the FRAM stuff,
interesting certainly (wasn't aware of that technology)..... My
application involves communications (continuous buffering of packets,
etc.), so non-volatility is unnecessary, and counter-driven
block-optimized addressing is actually a big plus, but I'm not at all
comfortable with devices having finite write cycle lifetime. I guess
I'm just suprised that regular static RAM for SPI type buses isn't a
big enough market to drive product development. Dave.


Re: Mid-capacity RAM with serial connection to MCU?
snipped-for-privacy@hotmail.com says...
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A couple of points to take a look at
    - I believe the wear out mode for FRAM is to become the equivalent
of a volatile SRAM (as you were initially looking for)
    - the newer and usually larger devices claim and unlimited write
cycle lifetime.

Robert

Re: Mid-capacity RAM with serial connection to MCU?
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I would rather thik of changing the MCU to the one that has the proper
amount of RAM on board.

There is MSP430F1611 with 10KB of RAM, F1610 with 5 KB, and there are
several cheap ARM chips with 8 or 16 KB RAM (or even more than that) -
Atmel, Philips.

It's generally not a good idea to connect RAM to the chip that was
designed to operate standalone.

Re: Mid-capacity RAM with serial connection to MCU?

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Some years ago there was a Dallas part DS1280 converting a
byte-wide memory to 3-wire serial (up to 512KBytes).
No idea, if it is still available.

Regards
Klaus


Re: Mid-capacity RAM with serial connection to MCU?

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Or you could use a small CPLD to make a simple parallel SRAM to SPI bridge.
I am starting up on similar project using FPGA to interface parallel SDRAM
to SPI. Micro would use SPI with defined addressing scheme to read and
write SDRAM.

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