參數(shù)資料
    型號: X68C75 SLIC
    英文描述: Port Expander and EE Memory(端口擴展,多重地址/數(shù)據(jù)總線,高速CMOS,微控制器外圍芯片)
    中文描述: 端口擴展和EE記憶體(端口擴展,多重地址/數(shù)據(jù)總線,高速的CMOS微控制器外圍芯片)
    文件頁數(shù): 3/28頁
    文件大小: 238K
    代理商: X68C75 SLIC
    3
    X68C75 SLIC
    E
    2
    PIN DESCRIPTIONS
    PIN NAME
    I/O
    DESCRIPTION
    A
    15
    –A
    8
    I
    Non-multiplexed high-order Address line inputs for the upper byte of the address. The addresses are
    latched when AS makes a HIGH to LOW transition.
    Multiplexed lower-order Address and DATA lines. The addresses are latched when AS makes a
    HIGH to LOW transition.
    Address Strobe input is used to latch the addresses present on the address lines A
    15
    –A
    8
    and AD
    7
    AD
    0
    into the device. The addresses are latched when AS transitions from HIGH to LOW.
    The device select (CE) is an active HIGH input. This signal has to be asserted prior to AS HIGH to
    LOW transition in order to generate a valid internal device select signal. Holding this pin LOW and
    AS LOW will place the device in standby mode. The ports stay active at all times.
    The E clock is the bus frequency clock input, and is used as a data timing reference signal. When
    the E clock is LOW, the addresses are latched by HIGH to LOW transition on the AS pin. The E
    clock HIGH cycle is used for data transfers.
    The
    IRQ
    is an open-drain output. It can be configured to signal latching of new data into the ports,
    and completion of
    an E
    2
    memory write cycle.
    The I/O lines of port A. The output driver can be configured as either CMOS or open-drain using the
    AWO bit in CR. The I/O direction bit (DIRA) in CR is used to select the port A I/O mode.
    The I/O lines of port B. The output driver can be configured as either CMOS or open-drain using the
    BWO bit in CR. The I/O direction bit (DIRB) in CR is used to select the port B I/O mode.
    The R/
    W
    signal indicates the direction of data transfers. During phase 2 (HIGH cycle) of the E clock,
    the R/
    W
    is HIGH for a read, and LOW for a write cycle.
    RESET
    is used to initialize the internal static registers and has no effect on the E
    2
    memory opera-
    tions. The default active level is LOW, but it can be reconfigured in EEM register.
    The
    SEL
    input should be LOW for the device to be selected. This input is normaly tied to V
    SS
    .
    The STRA controls port A and STRB controls port B. When ports are configured as inputs, a valid
    transition on their strobe pins will latch into their Port Data Register the data present at the port input
    pins. Writing to an output port Data Register generates a pulse of fixed duration on its corresponding
    strobe pin. The output data presented at the output pins stay valid until the next data is written to the
    output port data register.
    WC
    input has to be held LOW during a write cycle. It can be permanently tied HIGH in order to
    disable writes to the E
    2
    memory. Taking the
    WC
    HIGH prior to t
    BLC
    (100
    μ
    s; the time delay from the
    last write cycle to the start of internal programming cycle) will inhibit the write operation.
    AD
    7
    –AD
    0
    I/O
    AS
    I
    CE
    I
    E
    I
    IRQ
    O
    PA
    7
    –PA
    0
    I/O
    PB
    7
    –PB
    0
    I/O
    R/
    W
    I
    RESET
    I
    SEL
    STRA, STRB
    I
    I/O
    WC
    I
    2899 PGM T01.1
    The X68C75 write control input, serves as an external
    control over the completion of a previously initiated page
    load cycle.
    The X68C75 also features the industry standard 5V E
    2
    memory characteristics such as byte or page mode write
    and Toggle Bit Polling.
    Read
    A HIGH to LOW transition on AS latches the address;
    the data will be output on the AD pins when E clock and
    R/
    W
    are HIGH (t
    ACC
    ).
    Write
    A write is performed by latching the address on the
    falling edge of AS. The R/
    W
    signal LOW while E clock is
    HIGH initiates a write cycle. The valid data must be
    present on AD
    0
    -AD
    7
    prior to an E clock HIGH to LOW
    transition. The data will be latched into the X68C75 on
    the falling edge of E clock.
    Page Write Operation
    The X68C75 supports page mode write operations. This
    allows the microcontroller to write from one to thirty-two
    bytes of data to the X68C75. Each individual write within
    a page write operation must conform to the byte write
    timing requirements. The rising edge of E clock starts a
    timer delaying the internal programming cycle 100
    μ
    s,
    therefore, each successive write operation must begin
    within 100
    μ
    s of the last byte written. The waveform
    on page 19 illustrates the sequence and timing
    requirements.
    Toggle Bit Polling
    Because the X68C75 typical write timing is less than the
    specified 5ms, Toggle Bit Polling has been provided to
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