PRELIMINARY DATA SHEET
MSP 34x0D
4.1.2. Quadrature Mixers
4.1.3. Low-pass Filtering Block
for Mixed Sound IF Signals
The digital input coming from the integrated A/D con-
verter may contain audio information at a frequency
range of theoretically 0 to 9 MHz corresponding to the
selected standards. By means of two programmable
quadrature mixers, two different audio sources, for
example NICAM and FM-Mono, may be shifted into
baseband position. In the following, the two main
channels are provided to process either:
Data shaping and/or FM bandwidth limitation is per-
formed by a linear phase finite impulse response (FIR)
filter. Just like the oscillators’ frequency, the filter coeffi-
cients are programmable and are written into the IC by
the CCU via the control bus. Thus, for example, differ-
ent NICAM versions can easily be implemented. Two
not necessarily different sets of coefficients are
required, one for MSP-Ch1 (NICAM or FM2) and one
for MSP-Ch2 (FM1 = FM-mono). In a corresponding
table several coefficient sets are proposed.
– NICAM (MSP-Ch1) and FM/AM mono (MSP-Ch2)
simultaneously or, alternatively:
– FM-Mono (Ch2)
– FM2 (MSP-Ch1) and FM1 (MSP-Ch2).
Two programmable registers, to be divided up into a
low and a high part, determine frequency of the oscilla-
tor, which corresponds to the frequency of the desired
audio carrier.
DCO1
ADR
MSP3410D only
MODE_REG[6]
Oscillator
NICAMA
DQPSK
Decoder
NICAM
Decoder
FIR1
NICAMB
Phase
Phase and
AM Dis-
crimination
Mixer
Lowpass
Differen-
tiator
FM2
Mute
Lowpass
VREFTOP
MSP sound IF channel 1
(MSP-Ch1: FM2, NICAM)
Carrier
Detect
AD_CV[7:1]
AGC
Amplitude
IDENT
Mixer
ANA_IN1+
ANA_IN2+
AD_CV[9]
AD
Carrier
Detect
AD_CV[8]
MSP sound IF channel 2
(MSP-Ch2: FM1, AM)
Amplitude
ANA_IN-
Mute
Lowpass
FM1/AM
Phase and
AM Dis-
crimination
Mixer
Lowpass
FIR2
Differen-
tiator
Phase
MODE_REG[8]
FRAME
Pins
Oscillator
DCO2
Internal signal lines (see fig. 4–2)
Demodulator Write Registers
NICAMA
DCO2
Fig. 4–2: Architecture of demodulator and NICAM decoder section
Micronas
11
MICRONAS [ MICRONAS ]
