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  • 參數(shù)資料
    型號: PSD935G2-90UI
    廠商: 意法半導(dǎo)體
    英文描述: Configurable Memory System on a Chip for 8-Bit Microcontrollers
    中文描述: 在8片位微控制器可配置存儲系統(tǒng)
    文件頁數(shù): 28/91頁
    文件大?。?/td> 488K
    代理商: PSD935G2-90UI
    PSD935G2
    PSD9XX Family
    27
    The
    PSD935G2
    Functional
    Blocks
    (cont.)
    9.1.2 SRAM
    The SRAM is enabled when RS0
    the SRAM chip select output from the DPLD
    is high.
    RS0 can contain up to three product terms, allowing flexible memory mapping.
    The SRAM can be backed up using an external battery. The external battery should be
    connected to the Vstby pin (PE6). If you have an external battery connected to the
    PSD935G2, the contents of the SRAM will be retained in the event of a power loss. The
    contents of the SRAM will be retained so long as the battery voltage remains at 2V or
    greater. If the supply voltage falls below the battery voltage, an internal power switchover
    to the battery occurs.
    Pin PE7 can be configured as an output that indicates when power is being drawn from the
    external battery. This Vbaton signal will be high with the supply voltage falls below the bat-
    tery voltage and the battery on PE6 is supplying power to the internal SRAM.
    The chip select signal (RS0) for the SRAM, Vstby, and Vbaton are all configured using
    PSDsoft.
    9.1.3 Memory Select Signals
    The main Flash (FSi), secondary Flash (CSBOOTi), and SRAM (RS0) memory select
    signals are all outputs of the DPLD. They are defined using PSDsoft. The following rules
    apply to the equations for the internal chip select signals:
    1. Main Flash memory and secondary Flash memory sector select signals must
    not
    be
    larger than the physical sector size.
    2. Any main Flash memory sector must
    not
    be mapped in the same memory space as
    another Main Flash sector.
    3. A secondary Flash memory sector must
    not
    be mapped in the same memory space as
    another Flash Boot sector.
    4. SRAM and I/O spaces must
    not
    overlap.
    5. A secondary Flash memory sector
    may
    overlap a main Flash memory sector. In case of
    overlap, priority will be given to the Flash Boot sector.
    6. SRAM and I/O spaces
    may
    overlap any other memory sector. Priority will be given to
    the SRAM and I/O.
    Example
    FS0 is valid when the address is in the range of 8000h to BFFFh, CSBOOT0 is valid from
    8000h to 9FFFh, and RS0 is valid from 8000h to 87FFh. Any address in the range of RS0
    will always access the SRAM. Any address in the range of CSBOOT0 greater than 87FFh
    (and less than 9FFFh) will automatically address Boot memory segment 0. Any address
    greater than 9FFFh will access the Flash memory segment 0. You can see that half of the
    Flash memory segment 0 and one-fourth of Boot segment 0 can not be accessed in this
    example. Also note that an equation that defined FS1 to anywhere in the range of 8000h to
    BFFFh would
    not
    be valid.
    Figure 6 shows the priority levels for all memory components. Any component on a higher
    level can overlap and has priority over any component on a lower level. Components on
    the same level must
    not
    overlap. Level one has the highest priority and level 3 has the
    lowest.
    相關(guān)PDF資料
    PDF描述
    PSD935G2-A-20MI Configurable Memory System on a Chip for 8-Bit Microcontrollers
    PSD935G2-A-20U Configurable Memory System on a Chip for 8-Bit Microcontrollers
    PSD935G2-A-20UI Configurable Memory System on a Chip for 8-Bit Microcontrollers
    PSD935G2-A-70B81 Configurable Memory System on a Chip for 8-Bit Microcontrollers
    PSD935G2-A-70B81I Configurable Memory System on a Chip for 8-Bit Microcontrollers
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