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  • 參數(shù)資料
    型號(hào): MC44002P
    廠商: MOTOROLA INC
    元件分類: 消費(fèi)家電
    英文描述: CHROMA 4 VIDEO PROCESSOR
    中文描述: SPECIALTY CONSUMER CIRCUIT, PDIP40
    封裝: PLASTIC, DIP-40
    文件頁數(shù): 36/40頁
    文件大?。?/td> 491K
    代理商: MC44002P
    MC44002 MC44007
    FLAGS RETURNED BY THE MC44002/7
    36
    MOTOROLA ANALOG IC DEVICE DATA
    When the Address Read/Write bit is high the last two bytes
    of I2C data are read by the MCU as status flags; a listing of
    these may be found in Table 5. The MC44002/7 is designed
    to be part of a closed-loop system with the MCU; these flags
    are the feedback mechanism which allow the MCU to interact
    with the MC44002/7.
    A brief description of each of the flags, its significance and
    possible uses are given below.
    Table 5. Flags Returned
    Clock #
    Flag (Bit High)
    10
    Horizontal Flyback Present
    11
    Horizontal Drive Enabled
    12
    Horizontal Out Of Lock
    13
    Excess Average Beam Current
    14
    Less Than 576 Lines
    15
    Vertical Countdown Engaged
    16
    Overload Average Beam Current
    17
    Reserved
    18
    (Acknowledge)
    19
    Grid 2 Voltage Up Request
    20
    Grid 2 Voltage Down Request
    21
    OK
    22
    Fault
    23
    ACC Active
    24
    PAL Identified
    25
    SECAM Identified (MC44002 only)
    26
    Excess Peak Beam Current
    27
    (Acknowledge)
    Horizontal Flyback Present
    A sense of the horizontal
    flyback is taken via a current limiting series resistor from one
    of the flyback transformer secondaries to Pin 13. This is used
    for the H-phase shift control, but the presence of the pulse is
    also flagged to the MCU. Should the flag be missing after the
    chassis has been started up, then the MCU would have to
    shut down the set immediately.
    Horizontal Drive Enabled
    Indicates that the horizontal
    drive pulse output at Pin 15 has been enabled. This occurs
    after the stored values in the nonvolatile memory have been
    transferred to the MC44002/7 memory.
    Horizontal Out of Lock
    This flag is high when no valid
    signal is being received by the MC44002/7. Possible action in
    this case would be to change the phase detector gain and
    time constant bits to ensure rapid capture and locking to a
    new signal.
    Excess Average Beam Current
    This is one of two
    threshold levels which are determined by an external
    component network connected to the beam current sensing
    at Pin 9. This flag indicates an excess of beam current. A
    typical application of this flag in conjunction with “Overload
    Average Beam Current” flag is for the software controlled
    Automatic Beam Current Limiting. When this flag is “on”, it is
    recommended that the software prevent increases to the
    Contrast setting.
    Less Than 576 Lines
    – Output from the line counter in the
    vertical timebase. If there is a count of less than 576 this is
    indicative of a 525 line system being received. If the flag is
    low then a 625 line system is being received. This information
    can be used as part of an automatic system selection
    software.
    Vertical Countdown Engaged
    – The vertical timebase is
    based on a countdown system. The timebase starts in
    Injection Lock mode and when vertical retrace is initiated a
    4-bit counter is set to zero. A coincidence detector looks for
    counts of 625 lines. In Auto mode each coincidence causes
    the counter to count up. When eight consecutive
    coincidences are detected, the countdown is engaged. The
    MSB of the counter is used to set this flag to the processor.
    Overload Average Beam Current
    This is the second
    threshold level which is set by the external component
    network on Pin 9. The flag warns of an overload in anode
    current which should be lowered by reducing the Contrast.
    Grid 2 Voltage Up/Down Requests
    – These flags
    indicate when the RGB output loops are about to go out of the
    control range necessary for correct gray scale tracking.
    These 2 flags are used during factory adjustment.
    OK and Fault
    These two flags are included as a check
    on the communication line between the MCU and
    MC44002/7. The OK flag is permanently wired high and Fault
    is permanently wired low. The MCU can use these flags to
    verify that the data received is valid.
    ACC Active
    This flag is high when there is a sufficient
    level of burst present in PAL and NTSC modes during the
    video back porch period. The flag goes low when the level of
    burst falls below a set threshold or if the signal becomes too
    noisy. The flag is used to implement a software color killer in
    PAL and NTSC and is also available for system identification
    purposes. Since in SECAM there is line carrier present
    during the gating period, it is quite likely that the ACC will be
    on, or will flicker on and off in this mode.
    * PAL Identified
    Recognizes the line-by-line swinging
    phase characteristic of the PAL burst. When this flag is on
    together with the ACC flag, this is positive identification for a
    PAL signal.
    * SECAM Identified
    Senses the changing line-by-line
    reference frequencies (Fo1 and Fo2) present during the back
    porch period of the SECAM signal. This flag alone provides
    identification that SECAM is being received (MC44002 only).
    Excess Peak Beam Current
    A voltage threshold is set
    on the beam current feedback on Pin 20, which is also used
    for the RGB output loops for current sampling. When the
    threshold is reached, the flag is set, indicating too high a peak
    beam current which may be in only a part of the screen. The
    response of the MCU might be to reduce the contrast of the
    picture. This flag, together with the Excess Average Beam
    Current flag, performs the function of beam limiting. The
    exact way in which this is handled is left to the discretion of
    the user who will have their own requirements, which may be
    incorporated by the way in which the software is written.
    * These two flags are set in opposition to one another such that they can never both be on at the same time. This has been done to try to prevent misidentification from occurring. Often it is
    very difficult to distinguish between PAL and SECAM especially when broadcast material has been transcoded, sometimes badly, leaving e.g. large amounts of SECAM carrier in a
    transcoded PAL signal (also often with noise). With this method the strongest influence will win out making a misidentification much less likely.
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