Shop OBEX P1 Docs P2 Docs Learn Events
Does the propeller actually need and EXTERNAL EEPROM? — Parallax Forums

Does the propeller actually need and EXTERNAL EEPROM?

Chris_DChris_D Posts: 305
edited 2009-04-20 00:00 in Propeller 1
Hi guys,

I am a bit puzzled.· I will be building my first board using a prop (have been experimenting with the demo board) and am wondering if I need the external EEPROM.· The data sheet and manual seems to indicate that the chip has its own ROM, yet there are many references that seem to indicate you have to have an external EEPROM if you want the application to start up without having to download the program.

Chris
·

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-04-18 19:29
    The built-in ROM is masked and not rewritable. You do not need an external EEPROM if you want to reload code from your PC into the Prop's RAM every time you power it up. Otherwise, yes, you do need the external EEPROM.

    -Phil
  • Bob Lawrence (VE1RLL)Bob Lawrence (VE1RLL) Posts: 1,720
    edited 2009-04-18 19:34
    @ Chris_D

    This is what the internal ROM is used for: (taken from en.wikipedia.org/wiki/Parallax_Propeller )

    ROM extensions

    In addition to the Spin interpreter and a bootloader, the built-in ROM provides some data which may be useful for certain sound, video, or mathematical applications:

    * a bitmap font is provided, suitable for typical character generation applications (but not customizable);
    * a logarithm table (base 2, 2048 entries),
    * an antilog table (base 2, 2048 entries),
    * and a sine table (16-bit, 2049 entries).

    The math extensions are intended to help compensate for the lack of a floating-point unit as well as more primitive missing operations, such as multiplication and division (this is masked in Spin but is a limitation for assembly language routines). The propeller is a 32-bit processor, however, and these tables may not have sufficient accuracy for higher-precision applications.

    The internal RAM is volatile and you will loose any program (Asm or Spin programs) .that's loaded once the power is turned off. When you want to keep a program accessible even after the power is turned off you have to store it in the external l EEPROM .

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Aka: CosmicBob
  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2009-04-19 00:01
    You made the mistake of calling the internal ROM. ROM is non-volatile and this may be what is confusing you chris_d. Ram is volatile memory that will be erased every time the chip is reset or turned off.
    The propeller has a main hub RAM that is accessible by any of the cogs and each cog has it's own RAM that it can access via asm code.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Toys are microcontroled.
    Robots are microcontroled.
    I am microcontrolled.
  • tonyp12tonyp12 Posts: 1,951
    edited 2009-04-19 00:12
    The prop have internal ROM.

    The boot loader is stored there, so it know what to do when you first power it up.
    The reading from serial EEPROM is done through software

    and not something the prop would know to do without having internal software stored in ROM.



    If you order a few 1000's props, I'm sure Parallax lets you custom make your own Prop ROM.
    and the need for an external eeprom could be eliminated.

    But you would also loose the ability to make updates on your software, eg no new firmware updates.

    ·
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-19 00:17
    bet it would take more then a few thousand. I would not even bother asking unless you need more then 100,000

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • Chris_DChris_D Posts: 305
    edited 2009-04-19 11:29
    Yeah, that was what I was afraid of.· In this age of flash memory micros, is just seems kind of strange to need external EEPROM for program storage.· Oh well, it is what it is.

    Thanks guys

    Chris
  • LeonLeon Posts: 7,620
    edited 2009-04-19 13:03
    It depends on the fab process. Many simply don't allow flash to be on the same chip. For instance, TSMC doesn't have it on their 90 nm process but does on their 135 nm process.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-19 13:32
    on board flash would be nice but there are advantages to external. you can use a bigger ic if you need to. I know it is not much but its there.

    if space or just not wanting to deal with it I have designed a module with the flash eeprom and crystal on board. size is only 0.1" wider then the dip package.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2009-04-19 23:44
    flash would be a better memory source then an external EEPROM. It would be nice if the program read strait from the EEPROM,
    the advantage of this is that you can remove the memory source and not have to replace it until you reset or turned off the Propeller.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Toys are microcontroled.
    Robots are microcontroled.
    I am microcontrolled.
  • whickerwhicker Posts: 749
    edited 2009-04-20 00:00
    having an external eeprom allows you to select the size of external memory you need. obviously by default the first 32KB will be loaded on bootup.

    microcontrolled,

    the external eeprom for the time being, is based on flash technology. loading off of an external memory chip on bootup is hardly uncommon.
    the propeller program runs from RAM. this already allows the removal of the external eeprom until reset or powerup, for whatever reason.
Sign In or Register to comment.