MC92314 Datasheet, PDF (37/100 Pages) Motorola, Inc – DVB-T Single Chip Demodulator Application Note

Freescale Semiconductor, Inc.
Device Description
SYNC
(1 BYTE)
DATA
) (187BYTES
RS REMAINDER
(16 BYTES)
SYNC
(1 BYTE)
DATA
(187BYTES)
RS REMAINDER
(16 BYTES)
Pseudo Random Binary Sequence Period
(1504 BYTES)
SYNC
(1 BYTE)
Figure 3-11. MPEG-2 Frame Structure
3.2.3.3.3 Frame Synchroniser Modes
n ^{The Frame Synchroniser has two operation modes: the Acquisition and Tracking Modes. The}
tio ^{Acquisition Mode starts when an initial Sync Byte is detected and continues until a specified}
number of additional Sync Bytes has been found at the correct positions within a specified
a number of MPEG-2 transport packets. In this case the Tracking Mode is entered. The Frame
Synchroniser remains in the Tracking mode as long as the (different) set of synchronisation
rm ^{conditions for tracking is met and maintained. Four integer parameters (set through the I2C}
fo ^{Interface) are used to establish these two modes: Aq_Sync_Thresh, Aq_Ref_Thresh,}
Tr_Sync_Thresh and Tr_Ref_Thresh. Aq_Sync_Thresh and Aq_Ref_Thresh are used to set the
In ^{desired level of Acquisition conditions. If Aq_Sync_Thresh Sync Byte or inverted Sync Byte}
matches are found in Aq_Ref_Thresh frame spaced positions (e.g. Aq_Sync_Thresh = 2 and
y _{Aq_Ref_Thresh = 8: if 2 Sync Bytes are found in 8 MPEG-2 frames or in 8 x 204 = 1632 bytes),}
r _{In_Sync is signalled and the Tracking Mode is enabled. Otherwise, the correlation upon the input}
a _{bit stream is continued and the Frame Synchroniser further remains out of the synchronisation}
in _{state. In the Tracking Mode, Tr_Sync_Thresh Sync Byte or inverted Sync Byte matches are}
lim ^{necessary in Tr_Ref_Thresh frame spaced positions in order to stay In_Sync. See Figure 3-12}
for the state diagram of the Frame Synchroniser.
re _{The parameters Aq_Ref_Thresh (default: 8) and Tr_Ref_Thresh (default: 31) can be set}
P between 0 and 31 and the parameters Aq_Sync_Thresh (default: 2) and Tr_Sync_Thresh
(default: 3) can be set between 0 and 7.
Single Chip DVB-T Demodulator - Rev. 1.3 (11/30/98)
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MOTOROLA
3-19