SRAM vs DRAM

    Good morning all, I have a FANUC R30iA controller and wanted to understand some of my spare parts. I have one SRAM card (A05B-2500-H064) and one DRAM card (a05B-2500-H021), and I wanted some one to explain the purpose of these two cards inside my controller? This is for my own general understanding of the machine parts. Thank you!

    From the Karel manual:


    1.4.1 Memory

    Controller memory consists of three types of memory.


    • Dynamic random access memory (DRAM)

    DRAM memory is volatile. Memory contents do not retain their stored values when power is

    removed. DRAM memory is also referred to as temporary memory (TEMP).


    • A limited amount of battery-backed static/random access memory (SRAM).

    SRAM memory is nonvolatile. Older KAREL controllers used a CMOS implementation of SRAM.

    The KAREL programming language has many lexical references to CMOS, but the current technology

    used is non-CMOS SRAM. SRAM memory is also referred to as permanent memory (PERM). The

    TPP memory pool (used for TP programs) is allocated from PERM. A portion of permanent memory

    is set aside as a storage device called the memory file device (MF:). Since permanent memory can be

    set aside on SRAM, the controller further distinguishes SRAM memory as the RAM disk (RD:).


    • Flash memory (FROM)
    FROM memory is nonvolatile. A portion of permanent memory is set aside as a storage device

    called the memory file device (MF:). Since permanent memory can also be set aside on FROM, the

    controller further distinguishes FROM memory as the FROM disk (FR:).

    Additional off-line storage for archiving programs and data is also available as an optional feature.


    SRAM is battery backed. If you remove the controller battery with power off or remove the SRAM card itself, it is wiped. A simple image restore will get you going again.


    If FROM goes bad I believe an image restore is all that's needed.


    DRAM is volatile so doesn't matter. If it goes bad just swap it out and you are good.

    Is it safe to replace the SRAM + DRAM card with power on? Both sit on the main CPU A Board. With controller power on and backup battery plugged in, If I pull out the entire Main CPU A board, and swap out the SRAM and DRAM cards, hypothetically I should not lose anything, correct?

    No, you can't replace cards with power on.


    You should replace batteries with power on but not cards.


    If you need to replace both SRAM and DRAM cards:


    1. Take an image backup
    2. Power off
    3. Replace cards
    4. Power up into bmon and restore image

    For DRAM only you shouldn't need to restore the image as long as your controller battery is good. But always take an image backup as a precaution.

    Quote from alive15

    Good morning all, I have a FANUC R30iA controller and wanted to understand some of my spare parts. I have one SRAM card (A05B-2500-H064) and one DRAM card (a05B-2500-H021), and I wanted some one to explain the purpose of these two cards inside my controller? This is for my own general understanding of the machine parts. Thank you!


    Adding to HawkME's explanation:

    The A05B-2500-H064 is a FROM/SRAM module (64MB FROM /2MB SRAM). The software and programs are stored on this module. It must match the one you remove or the Image loaded in will be corrupt.

    The A05B-2500-H021 is the CPU/DRAM module containing the CPU and 64MB of DRAM. Nothing remains in DRAM once the power is turned off.

    The controller loads what it needs from the SRAM and FROM into the much faster DRAM to run. Having the DRAM on the same module as the CPU allows faster operation.

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