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    參數(shù)資料
    型號: BU-61583D1-401
    廠商: DATA DEVICE CORP
    元件分類: 微控制器/微處理器
    英文描述: 2 CHANNEL(S), 1M bps, MIL-STD-1553 CONTROLLER, CQIP70
    封裝: CERAMIC, DIP-70
    文件頁數(shù): 10/48頁
    文件大?。?/td> 378K
    代理商: BU-61583D1-401
    18
    Data Device Corporation
    www.ddc-web.com
    BU-61582
    G-08/02-250
    CIRCULAR BUFFER MODE
    FIGURE 6 illustrates the RT circular buffer memory management
    scheme. The circular buffer mode facilitates bulk data transfers.
    The size of the RT circular buffer, shown on the right side of the
    figure, is programmable from 128 to 8192 words (in even powers
    of 2) by the respective Subaddress Control Word. As in the sin-
    gle message mode, the host processor initially loads the individ-
    ual Lookup Table entries. At the start of each message, the
    SP’ACE stores the Lookup Table entry in the third position of the
    respective message block descriptor in the stack area of RAM,
    as in the Single Message mode. The SP’ACE transfers Receive
    or Transmit Data Words to (from) the circular buffer, starting at
    the location referenced by the Lookup Table pointer.
    At the end of a valid (or, optionally, invalid) message, the value of
    the Lookup Table entry updates to the next location after the last
    address accessed for the current message. As a result, Data
    Words for the next message directed to the same Tx/RX(/Bcst)
    subaddress will be accessed from the next contiguous block of
    address locations within the circular buffer. As a recommended
    option, the Lookup Table pointers may be programmed to not
    update following an invalid receive (or broadcast) message. This
    allows the 1553 bus controller to retry the failed message, result-
    ing in the valid (retried) data overwriting the invalid data. This
    eliminates overhead for the RT’s host processor. When the
    pointer reaches the lower boundary of the circular buffer (locat-
    ed at 128, 256, . . . 8192-word boundaries in the BU-61582
    address space), the pointer moves to the top boundary of the cir-
    cular buffer, as FIGURE 6 shows.
    IMPLEMENTING BULK DATA TRANSFERS
    The use of the Circular Buffer scheme is ideal for bulk data trans-
    fers; that is, multiple messages to/from the same subaddress.
    The recommendation for such applications is to enable the cir-
    cular buffer interrupt request. By so doing, the routine transfer of
    multiple messages to the selected subaddress, including errors
    and retries, is transparent to the RT’s host processor. By strate-
    gically initializing the subaddress’s Lookup Table pointer prior to
    the start of the bulk transfer, the BU-61582 may be configured to
    issue an interrupt request only after it has received the anticipat-
    ed number of valid Data Words to the designated subaddress.
    SUBADDRESS DOUBLE BUFFERING MODE
    For receive (and broadcast) subaddresses, the BU-61582 RT
    offers a third memory management option, Subaddress Double
    Buffering. Subaddress double buffering provides a means of
    ensuring data consistency. FIGURE 7 illustrates the RT
    Subaddress Double Buffering scheme. Like the Single Message
    and Circular Buffer modes, the Double Buffering mode may be
    selected on a subaddress basis by means of the Subaddress
    Control Word. The purpose of the Double Buffering mode is to
    provide the host processor a convenient means of accessing the
    most recent, valid data received to a given subaddress. This
    serves to ensure the highest possible degree of data consisten-
    cy by allocating two 32-bit Data Word blocks for each individual
    receive (and/or broadcast) subaddress.
    At a given point in time, one of the two blocks will be designated
    as the “active” 1553 data block while the other will be designat-
    ed as the “inactive” block. The Data Words from the next receive
    message to that subaddress will be stored in the “active” block.
    15
    13
    0
    RECEIVED
    (TRANSMITTED)
    MESSAGE
    DATA
    (NEXT LOCATION)
    POINTER TO
    CURRENT
    DATA BLOCK
    POINTER TO
    NEXT DATA
    BLOCK
    LOOK-UP TABLE
    ENTRY
    LOOK-UP TABLES
    LOOK-UP
    TABLE
    ADDRESS
    BLOCK STATUS WORD
    TIME TAG WORD
    DATA BLOCK POINTER
    RECEIVED COMMAND
    WORD
    CONFIGURATION
    REGISTER #1
    STACK
    POINTERS
    DESCRIPTOR
    STACK
    CURRENT
    AREA B/A
    1. TX/RX/BCST_SA look-up table entry is updated following valid receive (broadcast) message
    or following completion of transit message
    Notes:
    *
    50%
    CIRCULAR
    BUFFER
    ROLLOVER
    INTERRUPT
    100%
    CIRCULAR
    BUFFER
    ROLLOVER
    INTERRUPT
    CIRCULAR
    DATA BUFFER*
    (128,256,...8192 WORDS)
    FIGURE 6. RT MEMORY MANAGEMENT: CIRCULAR BUFFER MODE
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