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    參數(shù)資料
    型號: M38855F7-HP
    廠商: Renesas Technology Corp.
    英文描述: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
    中文描述: 單芯片8位CMOS微機(jī)
    文件頁數(shù): 67/103頁
    文件大?。?/td> 1580K
    代理商: M38855F7-HP
    3885 Group
    SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
    MITSUBISHI MICROCOMPUTERS
    66
    COMPARATOR CIRCUIT
    Comparator Configuration
    The comparator circuit consists of the ladder resistors, the analog
    comparators, a comparator control circuit, the comparator refer-
    ence input selection bit (bit 7 of PCTL2), a comparator data
    register (CMPD), the comparator reference power source input pin
    (P2
    0
    /CMP
    REF
    ) and analog input pins (P3
    0
    P3
    7
    ). The analog input
    pin (P3
    0
    P3
    7
    ) also functions as an ordinary digital port.
    Comparator Operation
    To activate the comparator circuit, first set port P3 to input mode
    by setting the corresponding direction register (P3D) to
    0
    to use
    port P3 as an analog voltage input pin. The internal fixed analog
    voltage (V
    CC
    29/32) can be generated by setting
    1
    to the com-
    parator reference input selection bit (bit 7 of PCTL2). The internal
    fixed analog voltage becomes about 2.99 V at V
    CC
    = 3.3 V. When
    setting
    0
    to the comparator reference input selection bit, the P2
    0
    /
    CMP
    REF
    pin becomes the comparator reference power source in-
    put pin and it is possible to input the comparator reference power
    source optionally from the external. The voltage comparison is im-
    mediately performed by the writing operation to the comparator
    data register (CMPD). After 14 cycles of the internal system clock
    φ
    (the time required for the comparison), the comparison result is
    stored in the comparator data register (CMPD).
    If the analog input voltage is greater than the internal reference
    voltage, each bit of this register is
    1
    ; if it is less than the internal
    reference voltage, each bit of this register is
    0
    . To perform an-
    other comparison, the voltage comparison must be performed
    again by writing to the comparator data register (CMPD).
    Read the result when 14 cycles of
    φ
    or more have passed after the
    comparator operation starts. The ladder resistor is turned on dur-
    ing 14 cycles of
    φ
    , which is required for the comparison, and the
    reference voltage is generated. An unnecessary current is not
    consumed because the ladder resistor is turned off while the com-
    parator operation is not performed. Since the comparator consists
    of capacitor coupling, the electric charge may lost if the clock fre-
    quency is low.
    Keep the clock frequency more than 1 MHz during the comparator
    operation. Do not execute the STP, WIT, or port P3 I/O instruction.
    Fig. 64 Comparator circuit
    V
    SS
    8
    8
    V
    CC
    P3 (8)
    P3
    7
    P3
    6
    P3
    0
    b0
    Comparator reference input selection bit
    (bit 7 of PCTL2)
    Comparator data register
    Compar-
    ator
    Ladder resistor
    connecting signal
    Comparator
    control circuit
    Comparator connecting
    signal
    Compar-
    ator
    Compar-
    ator
    P2
    0
    /CMP
    REF
    V
    CC
    29/32
    1
    0
    Data bus
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