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External memory assist — Parallax Forums

External memory assist

nick bernardnick bernard Posts: 329
edited 2005-12-23 14:36 in General Discussion
hello,
i could use some help selecting an external memory ic on an sx48 project as i am a nub in this area.
flash is nonvolitile & rewriteable (once a second, forever) correct?
nonvolitile, rewriteable, uses <27 control pins, & hand solerable are my only known prereq's.

i found this one at digikey
AT29C010A-70TC-ND IC FLASH MEM 5V 1M 70NS 32TSOP
it has mucho memory and is quick but requires many control pins.
but i can ignore some of the pages and reduce the number of address pins required right?

any help would be well received

rox on
nickB

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engineer, fireman, bowler, father, WoW addict [noparse];)[/noparse]

Comments

  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-12-22 22:13
    What size are you looking for, also is speed of transaction important? (IE is serial sufficent, or do you need the faster parallel access)

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  • nick bernardnick bernard Posts: 329
    edited 2005-12-22 22:34
    2kByte should suffice for this application, but future applications on this device could require much more.
    serial would suffice since this is a user interface and users are much slower that the sx series.
    i2c would be a delight but digikey only has a 256X8b i2c device in a 8dip package and its volitile, methinks. (PCF8570PN).
    i dont have any experiance with spi but i'd be willing to learn BUT digikey doesnt list ANY serial devices with a 5VDC supply. which is a great convienence.

    so to revise the list of prereq's
    nonvolitile, rewriteable, uses <27 control pins, hand solerable, 5VDC supply, >=2KBytes

    also i suppose a brief history of the project might help

    this origionally was a bs2pe application
    there is a transmitter that sends 96 bytes via ttl serial I9600-8N1 to a single receiver. there is one signivicant bit (bit0) in the byte. each bit is read and packed into the scratchpad for analysis which results in a 16byte display (50 seperate addressed lines stored in the eeprom) on an lcd (hence the non-volitile part).

    in this project there will be 2 transmitters operating independantly with the same serial interface.
    i need a new receiver to read both serial lines and process all 192bits into one of 98 16byte sentences to be displayed on an LCD.

    since the origional project i've begun using the SX28's and in this application i think i'll try an sx48. i'd like to store the lcd sentences and the status bits in the external memory.
    i think that the sx48 can meet these requirements but i may need to expand in the future so more memory would be handy.


    thx
    nickb

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    engineer, fireman, bowler, father, WoW addict [noparse];)[/noparse]
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-12-22 22:52
    I personally like the FRAM Ramtron offers, its just like EEPROM but no worries about # of rewrites or delay for writing, the FM24C16-S is an 2Kx8 I2C 8-SOIC 5V for $2.19 from www.newarkinone.com, and there is the FM24C64 which is the 8K version for $3.13 (there is also a 32k version). The SOIC package is surface mount, but it is still easily soldered, having a pin pitch of 0.05" (twice as dense as DIP). Sparkfun sells SOIC to DIP breakoutboards for under $2 to make breadboarding with the chip easier.

    There are also other EEPROMs in DIP package that are I2C, and I think Parallax sells one that fits the bill.

    Examples are 24LC16 (2K), 24LC32 (4K),...

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    Post Edited (Paul Baker) : 12/22/2005 11:06:52 PM GMT
  • nick bernardnick bernard Posts: 329
    edited 2005-12-23 14:36
    thx paul
    i'll try out those fram ic's. also thx for the newark reference

    roxon
    nickb

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    engineer, fireman, bowler, father, WoW addict [noparse];)[/noparse]
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