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    參數(shù)資料
    型號: TS87C51RD2-VCE
    廠商: Atmel
    文件頁數(shù): 25/84頁
    文件大?。?/td> 0K
    描述: IC MCU 8BIT 64K OTP 40MHZ 44VQFP
    標(biāo)準(zhǔn)包裝: 160
    系列: 87C
    核心處理器: 8051
    芯體尺寸: 8-位
    速度: 40/30MHz
    連通性: UART/USART
    外圍設(shè)備: POR,PWM,WDT
    輸入/輸出數(shù): 32
    程序存儲器容量: 64KB(64K x 8)
    程序存儲器類型: OTP
    RAM 容量: 1K x 8
    電壓 - 電源 (Vcc/Vdd): 4.5 V ~ 5.5 V
    振蕩器型: 內(nèi)部
    工作溫度: 0°C ~ 70°C
    封裝/外殼: 44-QFP
    包裝: 托盤
    2007-2012 Microchip Technology Inc.
    DS70292G-page 33
    dsPIC33FJ32GP302/304, dsPIC33FJ64GPX02/X04, AND dsPIC33FJ128GPX02/X04
    The Overflow and Saturation Status bits can
    optionally be viewed in the STATUS Register (SR) as
    the logical OR of OA and OB (in bit OAB) and the
    logical OR of SA and SB (in bit SAB). Programmers
    can check one bit in the STATUS register to
    determine if either accumulator has overflowed, or
    one bit to determine if either accumulator has
    saturated. This is useful for complex number
    arithmetic, which typically uses both accumulators.
    The device supports three Saturation and Overflow
    modes:
    Bit 39 Overflow and Saturation:
    When bit 39 overflow and saturation occurs, the
    saturation logic loads the maximally positive 9.31
    (0x7FFFFFFFFF) or maximally negative 9.31 value
    (0x8000000000) into the target accumulator. The
    SA or SB bit is set and remains set until cleared by
    the user application. This condition is referred to as
    ‘super saturation’ and provides protection against
    erroneous data or unexpected algorithm problems
    (such as gain calculations).
    Bit 31 Overflow and Saturation:
    When bit 31 overflow and saturation occurs, the
    saturation logic then loads the maximally positive
    1.31 value (0x007FFFFFFF) or maximally nega-
    tive 1.31 value (0x0080000000) into the target
    accumulator. The SA or SB bit is set and remains
    set until cleared by the user application. When
    this Saturation mode is in effect, the guard bits are
    not used, so the OA, OB or OAB bits are never
    set.
    Bit 39 Catastrophic Overflow:
    The bit 39 Overflow Status bit from the adder is
    used to set the SA or SB bit, which remains set
    until cleared by the user application. No saturation
    operation is performed, and the accumulator is
    allowed to overflow, destroying its sign. If the
    COVTE bit in the INTCON1 register is set, a
    catastrophic overflow can initiate a trap exception.
    3.8.3
    ACCUMULATOR ‘WRITE BACK’
    The MAC class of instructions (with the exception of
    MPY, MPY.N, ED and EDAC) can optionally write a
    rounded version of the high word (bits 31 through 16)
    of the accumulator that is not targeted by the instruction
    into data space memory. The write is performed across
    the X bus into combined X and Y address space. The
    following addressing modes are supported:
    W13, Register Direct:
    The rounded contents of the non-target
    accumulator are written into W13 as a
    1.15 fraction.
    [W13] + = 2, Register Indirect with Post-Increment:
    The rounded contents of the non-target accumu-
    lator are written into the address pointed to by
    W13 as a 1.15 fraction. W13 is then incremented
    by 2 (for a word write).
    3.8.3.1
    Round Logic
    The round logic is a combinational block that performs
    a conventional (biased) or convergent (unbiased)
    round function during an accumulator write (store). The
    Round mode is determined by the state of the RND bit
    in the CORCON register. It generates a 16-bit, 1.15
    data value that is passed to the data space write
    saturation logic. If rounding is not indicated by the
    instruction, a truncated 1.15 data value is stored and
    the least significant word is simply discarded.
    Conventional rounding zero-extends bit 15 of the accu-
    mulator and adds it to the ACCxH word (bits 16 through
    31 of the accumulator).
    If the ACCxL word (bits 0 through 15 of the accu-
    mulator) is between 0x8000 and 0xFFFF (0x8000
    included), ACCxH is incremented.
    If ACCxL is between 0x0000 and 0x7FFF, ACCxH
    is left unchanged.
    A consequence of this algorithm is that over a succes-
    sion of random rounding operations, the value tends to
    be biased slightly positive.
    Convergent (or unbiased) rounding operates in the
    same manner as conventional rounding, except when
    ACCxL equals 0x8000. In this case, the Least
    Significant bit (bit 16 of the accumulator) of ACCxH is
    examined:
    If it is ‘1’, ACCxH is incremented.
    If it is ‘0’, ACCxH is not modified.
    Assuming that bit 16 is effectively random in nature,
    this scheme removes any rounding bias that may
    accumulate.
    The SAC and SAC.R instructions store either a
    truncated (SAC), or rounded (SAC.R) version of the
    contents of the target accumulator to data memory via
    the X
    bus, subject to data
    saturation
    (see
    the MAC class of instructions, the accumulator write-
    back operation functions in the same manner,
    addressing combined MCU (X and Y) data space
    though the X bus. For this class of instructions, the data
    is always subject to rounding.
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