MT312C ZARLINK [Zarlink Semiconductor Inc], MT312C Datasheet - Page 24

• Manufacturer Part Number: MT312C
• Description: Satellite Channel Decoder
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

MT312
4 Tuner Control
4.1 Simple Channel Change Sequence
If the MT312 is running, to change channel keeping
the same signal conditions, it is only necessary to
change the tuner data and possibly the DiSEqC™
data. NO reset is necessary.
4.2 Channel Change Sequence with a new
Symbol Rate
If the MT312 is running, to change channel and
Symbol rate but not Viterbi coding rate, change the
tuner data and possibly the DiSEqC™ data and
Symbol rate. NO reset is necessary.
4.3 Channel Change Sequence with Search
Mode
If the signal parameters are unknown, it is possible to
instruct the MT312 to find a digital signal and report
the parameters found. Registers 24 and 25 are
programmed with the expected range(s) and the
search mode bit SYM RATE[B15] is set high. A code
rate search is forced by programming more than one
bit in VIT MODE (26) register. The IQ spectrum
phase can be automatically determined by setting bit
7 in the VIT MODE (26) register.
Note: code rate 6/7 is not searched for DVB mode.
If a signal with the specified symbol rate range (or
ranges) is not found in the frequency range
searched, a QPSK Baud End interrupt (Bit B6, QPSK
INT L (2)) is issued.
When the MT312 QPSK section has locked to the
signal, this is indicated in register (6) by QPSK STAT
H[B0] = 1. The symbol rate found can be read from
registers (123 - 124) MONITOR, provided the
register (103) MON CTRL = 3. The tolerance of the
result is ±0.25%. The 14 MSBs of this result
(discarding two LSBs) may be written as the 14 LSBs
of the 16-bit register pair (23 and 24) SYM RATE in
the non-search mode for re-acquisition of the same
channel.
The FEC is locked to the signal, when the Byte Align
lock in FEC STATUS[B2] = 1. Then the code rate
found can be read from FEC STATUS[B6-4], see
register 6 49 for details.
24
Tuner Control
Figure 17 - Channel change sequence with new
Figure 16 - Simple channel change sequence
Program tuner via GPP in 'pass through mode'
Program tuner via GPP in 'pass through mode'
send TUNER DATA via I2C bus (5 bytes).
send TUNER DATA via I2C bus (5 bytes).
open port with Reg 20 = 64 (40hex)
open port with Reg 20 = 64 (40hex)
Symbol rate, DVB mode
eg V_IQ swap not set, CR = 5/6:
eg Horizontal with 22kHz on:
close port with Reg 20 = 0
eg Vertical with 22kHz on:
close port with Reg 20 = 0
Signal input - Symbol rate
Reg 22 = 65 (41hex)
Reg 23 = 22 (16hex)
Reg 22 = 1 (01hex)
Reg 25 = 8 (8hex)
Re-acquire signal
Re-acquire signal
Viterbi code rate
eg 22.0 MBaud:
DiSEqC mode
DiSEqC mode
Reg 27 = 1
Reg 24 = 0
Reg 27 = 1
GO
GO