MT312 Zarlink Semiconductor, MT312 Datasheet - Page 59

• Manufacturer Part Number: MT312
• Description: Satellite Channel Decoder
• Manufacturer: Zarlink Semiconductor

10.3
MOCLK will be a continuously running clock once symbol lock has been achieved in the QPSK block and is derived
from either the system clock or MICLK if external clock is selected. MOCLK is the MPEG data byte rate clock, the
internal rate is calculated from the formulae in section 10.4. The maximum movement in the packet synchronisation
byte position is limited to ± one output clock period.
All output data and signals (MDO[7:0], MOSTRT, MOVAL, BKERR) change on the negative edge of MOCLK
(MCLKINV = 1) to present stable data and signals on the positive edge of the clock. A complete packet is output on
MDO[7:0] on 188 (DVB) or 130 (DSS) consecutive clocks and the MDO[7:0] pins will remain low during the inter
packet gaps. MOSTRT goes high for the first byte clock of a packet. MOVAL goes high on the first byte of a packet
and remains high until the 188th byte (DVB) or 130th byte (DSS) has been clocked out.
BKERR has two modes of operation, selected by ERR_IND bit 7 of MON_CTRL register 103, see page 63.
10.3.1
When ERR_IND is Low:
Figure 21 above shows lock being lost while ERR_IND is low. The event is divided into five significant periods:
1. Packets being received without errors.
2. Packets being received with errors.
3. Signal too poor for any packets to be received (lost lock).
4. Lock regained but packets still have errors.
5. Packets being received again with no errors.
MPEG/DSS Data Output Signals
ERR_IND = 0
MDO[7:0] bus. BKERR goes low on the first byte of a packet where uncorrectable
bytes are detected and will remain low until the 188th byte (DVB) or 130th byte (DSS)
has been clocked out. BKERR also goes high when there is no de-scrambler lock, i.e.
there are no MPEG packets being output.
BKERR remains high when error free MPEG packets are being output on the
Figure 21 - BKERR example when ERR_IND is low
Zarlink Semiconductor Inc.
MT312
59
Design Manual