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Adding RAM — Parallax Forums

Adding RAM

KenLemKenLem Posts: 94
edited 2006-02-08 21:45 in General Discussion
I'd like to add 128Kb (16kx8) RAM to a microcontroller project but don't know what to use.· Any suggestions?

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Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-02-08 16:26
    Lots of people are using FRAMs -- they connect via I2C (access is like a standard I2C EEPROM), but are supposed to be faster.

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    Jon Williams
    Applications Engineer, Parallax
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-02-08 17:14
    FRAM reads are no faster than an equivalent EEPROM (the speed is dictated by the serial communications), but writes are faster because there is no programing delay like there is for EEPROM. FRAM also can be rewritten practically an infinite number of times unlike EEPROM.·Ramtron is the company which manufacturers FRAM. MRAM is another name for the technology and many companies are experimenting with the technology (Honeywell, Infineon, Freescale and Sony to name a few), but most do not have commercial products availible (Freescale has a pre-production 16 bit parallel MRAM).

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  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-02-08 17:20
    Sorry, Paul, my mistake -- I'm not sure why now, but I was under the impression they could run on a faster buss.

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    Jon Williams
    Applications Engineer, Parallax
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-02-08 17:38
    You could be correct, I have to look at the docs from Ramtron (and competing EEPROM chips) to see what speed of I2C is supported (in comparison with EEPROMs). I know you can get SPI FRAMS from them capable of a 25MHz clock speed.

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    ·1+1=10
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-02-08 17:45
    Ok Ramtron's I2C FRAMs support a 1MHz bus speed across the board, the only I2C EEPROMs which are not Standard Mode (100kHz) or Fast Mode (400kHz) are Microchip's 24FC series which supports 1MHz bus speed as well (1 MHz = High Speed Mode ?).

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  • BeanBean Posts: 8,129
    edited 2006-02-08 18:33
    If you need fast ram. I have used the Cypress CY62256 SRAM (256Kb, 32Kx8) it is 70ns but requires 26 I/O pins.
    It's very simple to address though, just put the address on the ports and read back the data on another port.
    Digikey has them. $2.50 - $3.00 for onesies.
    Bean.

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    Product web site: www.sxvm.com

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    ·
  • KenLemKenLem Posts: 94
    edited 2006-02-08 18:54
    Thanks for the part number Bean. I can deal with the 26 pins.


    This is what I found.

    CY7C1399B-15VC
    IC SRAM 32KX8 3.3V ASYNC 28-SOJ

    1 - 1.89
    25 - 1.51
    100 - 1.71


    I looked at the ramtron FRAM but it's more expensive.

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  • KenLemKenLem Posts: 94
    edited 2006-02-08 19:22
    The CY7C1399B-15VC·is the same size as CY62256 but cheaper.· Cypress website shows the CY7C1399B status as restricted.

    I wonder what the differences between the 2 chips are?

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    Speech & Video IC's for BasicStamps
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-02-08 19:26
    Sorry for the misunderstanding, most people only have a few pins to spare for external memory so we ussually suggest I2C or SPI EEPROM or FRAM. I have used the Cypress line as well with great success, its extremely fast and cheap. If you are going into production using Cypress memory, be careful which you choose, they have been discontinuing quite a few of thier chips (my favorite 128x8Kb of thiers was discontinued last Jan 1st).

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    ·1+1=10
  • KenLemKenLem Posts: 94
    edited 2006-02-08 19:27
    Cyress Website says:


    CY7C1399B

    Products : Memory : Async SRAMs : CY7C1399B

    256K (32K x 8) Static RAM

    Features

    Single 3.3V power supply
    Ideal for low-voltage cache memory applications
    High speed
    10/12/15 ns
    Low active power
    216 mW (max.)
    Low-power alpha immune 6T cell
    Plastic SOJ and TSOP packaging



    CY62256

     Products : Memory : Wafer & Die : CY62256

    256K (32K x 8) Static RAM

    Features

    Temperature Ranges
    Commercial: 0°C to 70°C
    Industrial: -40°C to 85°C
    Automotive: -40°C to 125°C
    High speed: 55 ns and 70 ns
    Voltage range: 4.5V-5.5V operation
    Low active power (70 ns, LL version, Com'l and Ind'l)
    275 mW (max.)
    Low standby power (70 ns, LL version, Com'l and Ind'l)
    28 µW (max.)
    Easy memory expansion with /CE and /OE features
    TTL-compatible inputs and outputs
    Automatic power-down when deselected
    CMOS for optimum speed/power
    Package available in a standard 450-mil-wide (300-mil body width) 28-lead narrow SOIC, 28-lead TSOP-1, 28-lead reverse TSOP-1, and 600-mil 28-lead PDIP packages
    Also available in lead-free packages



    The CY7C1399B looks faster, cheaper and 3.3V which is fine by me.

    Bean, does that make sense to you? Maybe you should add some RAM to your video device and get hi-res or color.

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  • BeanBean Posts: 8,129
    edited 2006-02-08 19:34
    Hey if you can stand lead-free the CY7C1399B-15ZXC is even cheaper.

    Yeah I would love to add RAM to the video modules, but too damn busy...

    I haven't found an easy way to do color NTSC, I could do VGA, but I don't know if that would fly ?

    Bean.

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    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    "SX-Video OSD module" Now available from Parallax for only·$49.95
    http://www.parallax.com/detail.asp?product_id=30015

    Product web site: www.sxvm.com

    "Ability may get you to the top, but it takes character to keep you there."
    ·
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-02-08 19:35
    Restricted means no longer availible as I was warning about. If you click on choose columns and click on Order Entry Closed, Prune Notification and Shipping Closed you see a 6 month span where a Prune Notification was sent to the distributors, 3 months later Orders were no longer accepted, then 3 months later no further shipments occured.

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    ·1+1=10
  • KenLemKenLem Posts: 94
    edited 2006-02-08 21:45
    Sorry Paul. I didn't see your message about restricted as I writing a reply. I take your point.· I'll be sure to check status of anything I want to use.

    The CY7C1399B-15ZXC looks acceptable. I don't understand your point about lead free. Excuse my inexperience but is there some additional hassle with lead free parts?

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    Speech & Video IC's for BasicStamps

    Post Edited (KenLem) : 2/8/2006 9:53:43 PM GMT
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