GS1501-CQR 查看數據表（PDF） - Gennum -> Semtech
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GS1501-CQR Datasheet PDF : 15 Pages
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3. DETAILED DESCRIPTION
3.1 DATA INPUT AND OUTPUTS
Data enters and exits the device synchronous to the rising
edge of PCLK_IN as shown in Figure 1.
3.2 INPUT BLANKER
Data words entering the GS1501 can be dynamically set to
Luma and Chroma blanking levels if desired as shown in
Figure 3. Blanking is applied to both the LUMA and
CHROMA channels simultaneously.
3.3 FIFO
The device does not flag transmission errors which might
exist in the ANC data packages. The internal FIFO is 1024
words deep for each of LUMA and CHROMA channels. For
those formats where the HANC region is greater than 1024
words, the user must take steps to ensure the FIFO does
not overflow, otherwise data may be lost. The GS1501
provides status signals to indicate the current content level
of the internal FIFO buffers, as described in section 3.1.
3.3.1 FIFO Status Bits
The device provides a status output signal FF_STA[2:0] that
indicates the state of the current content level of the internal
FIFOs. FF_STA[2:0] outputs 110, should the user supplied
ANC data have completely filled the internal FIFO buffer. It
is noted that once the internal FIFO is full, any attempt to
write data into the FIFO will cause the FIFO to overrun. The
device flags this overrun state by setting FF_STA[2:0]=111.
FF_STA[2:0] outputs 001, should all ANC data in the FIFO
be extracted and inserted into the video stream and the
internal FIFO becomes empty. It is noted that once the
internal FIFO is empty, any attempt to read data from the
FIFO will cause the FIFO to underrun. The device flags this
underrun state by setting FF_STA[2:0]=000 and no data is
inserted into the video stream. When ANC_Y/C is high,
FF_STA indicates the status of the LUMA FIFO buffer and
when ANC_Y/C is low, FF_STA indicates the status of the
CHROMA FIFO buffer.
It is important that the FIFO status flags are as up-to-date
as possible. Therefore, certain FIFO status flags are
synchronized with respect to W_CLK, and others are
synchronized with respect to PCLK_IN. During a write
cycle, status flags controlled by W_CLK experience a three-
cycle latency with respect to W_CLK. During a read cycle,
status flags controlled by PCLK_IN experience a three-
cycle latency with respect to PCLK_IN. This information is
summarized in Table 1, and illustrated in Figures 5 to 14.
NOTE: If a simultaneous FIFO read and write operation is to
be performed, the FF_STA[2:0] outputs should not be used
as they may indicate incorrect FIFO status.
3.3.2 FIFO Write Control
The FIFO control signal WEN is the write enable signal used
to enable the loading of ANC data into the internal FIFO by
the user through the FIFO interface. Note that the device
only allows loading to one of the two internal FIFO buffers
through the FIFO interface at a time. When ANC_Y/C is
high, the LUMA FIFO may be loaded. When ANC_Y/C is
low, the CHROMA FIFO may be loaded.
When the internal FIFO is not in the full or overrun states, it
is ready to accept ANC data. This should prompt the user
to supply up to 1024 data words to the FIFO by writing them
through the FIFO interface. Upon seeing a rising edge on
W_CLK, the device will accept the word being presented on
ANC_IN[9:0] into the selected FIFO. Each time W_CLK is
toggled, the internal write address pointer (LUMA or
CHROMA) is incremented while WEN is low. If WEN is high,
the write address pointer is not incremented and writing to
the FIFO is disabled.
3.3.4 FIFO Read Control
The FIFO control signal REN is the read enable signal used
to enable ANC data insertion from the internal LUMA or
CHROMA FIFO buffer into its corresponding video stream,
depending on the value of ANC_Y/C. The read address
pointer increments with the internal clock at the video data
rate while REN is low. If REN is high, the read address
pointer will not increment. Both address pointers for read
and write can be reset to their starting positions by toggling
the FIFO reset signal FFRST from high to low.
The device will insert the ANC data into the video streams
whenever data is present in the respective FIFO buffer and
the control signal REN is low. ANC data will be extracted
from the internal FIFO buffer and inserted into the video
stream until it is completely empty. When all words have
been read from the FIFO, the FF_STA[2:0] signal will be set
to 001.
3.3.4 ANC/Data Insertion
In many cases, the user only wants to insert ANC data into
the HANC region. In order to make this frequently used
mode easy, the device provides an automated insertion
mode. When the control signal FM_I/E is high, the FIFO
control signals FFRST and REN cannot be used for the
purpose described above. In this mode of operation, the
device generates these reset and enable signals internally,
which allows an automated insertion of ANC data into the
HANC region of the incoming LUMA or CHROMA data
streams. The user still needs to supply a proper WEN signal
to enable the loading of ANC data into the FIFO. Up to 1024
ANC data words of each of the LUMA or CHROMA FIFO(s)
9
GENNUM CORPORATION
52234 - 4
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