LMH0030_0608 Datasheet, PDF (11/29 Pages) National Semiconductor (TI) – SMPTE 292M/259M Digital Video Serializer with Video and Ancillary Data FIFOs and Integrated Cable Driver

Device Operation (Continued)
CONTROL DATA WRITE FUNCTIONS
Figure 2 shows the sequence of clock and control signals for
writing control data to the ancillary/control data port. The
control data write mode is similar to the read mode. The
control data write mode is started by making both the ANC/
CTRL input low and the RD/WR input low. Next, the 8-bit
address of the control register set to be accessed is placed
on port bits AD[7:0]. When a control register write address is
being written to the port, AD[9:8] must be driven as 00b
(0XXh, where XX are AD[7:0]). Toggle ACLK. The address is
captured on the rising edge of ACLK. Remove the address
after clocking it into the device on or before the falling edge
of ACLK. Observe the port input hold timing specification.
Next, the control register data is placed on the AD[7:0] port.
ACLK is again toggled. The data is written to the selected
register on the rising edge of ACLK. When control data is
being written to the port, AD[9:8] must be driven as 11b
(3XXh, where XX are AD[7:0]). Remove the register data
after clocking it into the device on or before the falling edge
of ACLK. Observe the port input hold timing specification.
Example: Setup (without enabling) the TPG Mode via the
AD port using the 1125 line, 30 frame, 74.25MHz, interlaced
component (SMPTE 274M) color bars as test pattern. The
TPG may be enabled after setup using the Multi-function I/O
port or by the control registers.
1. Set ANC/CTRL to a logic-low.
2. Set RD/WR to a logic-low.
3. Present 00Dh to AD[9:0] as the Test 0 register address.
4. Toggle ACLK.
5. Present 327h to AD[9:0] as the register data.
6. Toggle ACLK.
FIGURE 2. Control Data Write Timing
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ANCILLARY DATA FUNCTIONS
The LMH0030 can multiplex Ancillary Data into the serial
component video data stream. The ancillary data packet
structure, formatting and control words are given in standard
SMPTE 291M. The data may reside in portions of the hori-
zontal and vertical blanking intervals. The data can consist of
different types of message packets including audio data. The
LMH0030 supports ancillary data in the HANC and VANC
areas of standard definition component video and in the
chrominance channel (C’r/C’b) only for high-definition opera-
tion. As it applies to embedded (multiplexed) audio data, this
function follows the recommended practice for AES/EBU
default Level A data handling.
Figure 3 shows the sequence of clock, data and control
signals for writing Ancillary Data to the port. In ancillary data
write mode, 10-bit ancillary data is written into the AD[9:0]
port and subsequently into the ancillary data FIFO. From the
FIFO, the ancillary data can be inserted into the ancillary
data areas in the serial video data stream. Ancillary data may
be written to the FIFO only when in the ancillary data mode.
Ancillary data cannot be read from the FIFO through the AD
Port.
The process of loading ancillary data into the FIFO is done
during the active video portion of the video line. Occurrence
of the active video line interval is indicated by the H-bit in the
fourth word of the TRS sequence. The H-bit is available on
I/O Port bit-2.
The ancillary data write process begins by making the ANC/
CTRL input high and the RD/WR input low. Next, the data
words are presented to the port in sequence as specified in
SMPTE 291M beginning with the DID word. Data presented
to the port within the required setup and hold time param-
eters will be written into the FIFO on the rising edge of
ACLK. The user has the option of including a checksum in
the ANC input data or of having the LMH0030 calculate and
append the checksum. The LMH0030 will append the Ancil-
lary Data Flag to each packet automatically before multiplex-
ing with the video data.
The process of writing ancillary data to the FIFO is effectively
a double-buffered write operation. Therefore, in order to
properly write the last word of the data packet, the CRC,
whether supplied with the ANC data packet or internally
generated, to the FIFO, ACLK must be toggled two addi-
tional times after the last data word is clocked into the port
(or when the CRC is being generated internally and ap-
pended). In the case where multiple packets are being
loaded to the FIFO, the additional clocks are issued after the
last word of the final packet is received by the port.
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