CXD1961AQ Просмотр технического описания (PDF) - Sony Semiconductor
Номер в каталоге
Компоненты Описание
производитель
CXD1961AQ Datasheet PDF : 33 Pages
| |||
CXD1961AQ
(5) Auto Gain Control
By comparing the demodulated I/Q amplitude (I2 + Q2) and the reference level which is set via CPU I/F register
21 (hex), the AGC control signal is generated as PWM output at Pin 68. The polarity of the AGC can be
reversed by setting CPU I/F register 10 (hex). For the Tuner interface, see the reference circuit (4).
(6) Viterbi Decoder
The punctured decoding and Viterbi decoding are performed on the demodulated I and Q data. The punctured
rate is programmable from 1/2 to 7/8. When punctured mapping is performed, Viterbi lock flag at CPU I/F
register 09 (hex) goes one. Bit error count at QPSK demodulator output is estimated and output to CPU I/F
register 03, 04 (hex) as 16 bit data.
(7) Frame synchronization and Deinterleaver
By detecting the MPEG2 sync word 47 (hex), the synchronization of the data packet is achieved, and the
convolutional deinterleaver then recovers the original data order.
(8) Reed-Solomon Decoder
In DVB systems, 16 parity bytes are added to the 188 data bytes, so that up to 8 error bytes are correctable by
the Reed-Solomon decoder. If there are more than 8 error bytes in a packet, error correction is not performed
and the packet error flag PKTERR (Pin 28) goes high during the packet to indicate that the packet is not
correctable. The MSB of the second byte of the uncorrectable packet also becomes one. Bit error count at
Viterbi decoder output is estimated and output every 1280 packet (=204 × 8 × 1280 bit) to CPU I/F register 06,
07 (hex) at a resolution of 16 bits.
(9) Energy Dispersal Descrambler
Energy dispersal descrambling is represented by the polynomial X15 + X14 + 1. The initial sequence is loaded
when an inverted MPEG sync word B8 (hex) is detected. When MPEG sync word including inverted one is
detected every 204 bytes, the lock flag of the whole IC "FSYNC" goes high. FSYNC is output at Pin 83 and
CPU I/F register 09 (hex).
–4–
Share Link: 