QPSK Demodulator MT312
B3:
B2:
B1:
B0:
Reserved High = QPSK FR UNLOCK
High = QPSK calculation complete
High = QPSK TS MAX
High = QPSK CS MAX
Reading an Interrupt register resets that register.
Def
hex
NAME
ADR
B7
B6
B5
B4
B3
B2
B1
B0
QPSK INT L
02
QPSK INT [7:0] Interrupt QPSK (low byte)
R
00
The majority of these interrupts are for diagnostic purposes and generally not useful in normal operation,
unless otherwise indicated.
B7:
B6:
B5:
B4:
B3:
B2:
B1:
B0:
High = QPSK state change
High = QPSK frequency end of search rangeimportant indicator.
High = QPSK BAUD end of rangeimportant indicator.
High = QPSK AFC success
High = QPSK AFC fail
High = QPSK next frequency search
High = QPSK same frequency search
High = QPSK LTV limit
Reading an Interrupt register resets that register.
Frequency and symbol rate search is carried out as follows. If the symbol rate is known then MT312 will search
the specified frequency range for this symbol rate. Once the end of this range has been reached, "QPSK end of
frequency range search" interrupt will be issued and MT312 will resume the search beginning from frequency
zero. A "QPSK end of Symbol rate range(s) search" interrupt will not be issued.
If the symbol rate is not known, then MT312 can be made to search several sub-ranges of symbol rates, by
setting 12 bits of the pair of SYM RATE registers, as described in section 4.4. For illustration purposes, assume
that the symbol rate sub-ranges SYS CLK/2 to SYS CLK/3 and SYS CLK/4 to SYS CLK/6 are to be searched.
Then MT312 will begin the search from the upper sub-range SYS CLK/2 to SYS CLK/3. MT312 will search for
a channel with a symbol rate in this range over the specified frequency range, for example ± 10 MHz. If no
channel is found then MT312 will issue a "QPSK end of frequency range search" interrupt and will go on to
search the sub-range SYS CLK/4 to SYS CLK/6 over the specified frequency range. If no channel is found,
then MT312 will issue a "QPSK end of frequency range search" interrupt as well as a "QPSK end of Symbol
rate range(s) search" interrupt. Then MT312 will return to search the specified frequency range for a symbol
rate in the range SYS CLK/2 to SYS CLK/3. This process continues indefinitely, unless it is interrupted by host
processor software.
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