Altera Serial Digital Interface (SDI) MegaCore Function - Manual (Page 35)

Chapter 3: Functional Description 3–5
Block Description
February 2013 Altera Corporation Serial Digital Interface (SDI) MegaCore Function
User Guide
The CRC is calculated for all words in the active digital line, starting with the first
active word line and finishing with the final word of the line number (LN1). The initial
value of the CRC is set to zero, then the polynomial generator equation
CRC(X) = X
18 + X 5 + X 4 + 1 is applied.
The HD-SDI CRC module implements the CRC calculation by iteratively applying the
polynomial generator equation to each bit of the output data, processing the LSB first.
For correct CRC generation and insertion, the tx_trs signal must be asserted for the
first word of both EAV and SAV TRS (refer to
Figure 3–31 on page 3–47 and
Figure 3–32 on page 3–48 ).
Scrambling and NRZI Coding
SMPTE292M section 5 and SMPTE292M section 7 define a common channel coding
that is used for both SDI and HD-SDI. This channel coding consists of a scrambling
function (G
1
(X) = X 9 + X 4 + 1) followed by NRZI encoding (G
2
(X) = X + 1). The
scrambling module implements this channel coding. You can configure the module to
process either 10-bit or 20-bit parallel data.
The scrambling module implements the channel coding by iteratively applying the
scrambling and NRZI encoding algorithm to each bit of the output data, processing
the LSB first. Figure C.1 of SMPTE259M shows how the algorithm is implemented.
Transceiver Clock
Figure 3–3 shows the clocking scheme for the transmitter.
The tx_serial_refclk1 is an optional port that is enabled when you turn on the
Enable TX PLL select for 1/1.000 and 1/1.001 data rate reconfiguration
in the SDI
parameter editor.
Figure 3–3. Transmitter Clocking Scheme
Protocol Block (Transmitter) Transceiver Interface Block Transceiver Block
ALTGXB
tx_pclk
encoded_data[19:0]
txdata[19:0]
tx_pclk
pll_inclk
pll_inclk1
cal_blk_clk
reconfig_clk
gxb_txword[19:0]
gxb_tx_core_clk tx_clkout
(optional)
gxb_tx_clkout
sdi_tx
(serial data out)
tx_pclk
tx_serial_refclk
tx_serial_refclk1
gxb2_cal_clk
sdi_reconfig_clk