NXR-901
20
CIRCUIT DESCRIPTION
■
Modem control MPU
The modem control MPU (IC325) is 16-bit single chip
microprocessor incorporating 256K bytes of ROM and 20K
bytes of RAM.
This MPU controls the Flash memory, two DSPs, the
OCXO unit in the Transmitter unit (X42-328) and the PLL cir-
cuit.
It also monitors the external power supply voltage. If the
voltage is abnormal, it stops the system.
■
RX DSP (IC323)
In digital mode, the IF signal input from the ADC (IC312)
to the RX DSP is limited to a very narrow band. So, it passes
through the IF band limitation band.
This signal is demodulated by the wave detection pro-
cessing par t. The demodulated wave is made to pass
through the baseband limitation filter (root nyquist cosine
fi lter and 1/sinc fi lter).
This signal is symbol-detected and bit-judged, and is
then converted to digital data. Its frame timing is detected
and decoded for CAI data error correction.
Sound data is vocoder decode processed by the IC324
TX_Vocoder_DSP. It is then converted into the PCM signal.
It is analog-output as an audio signal by the DAC part of
the Audio codec IC (IC309 AOUTL terminal).
Main
MPU
IC703
(Compact
Flash)
LAN IC
IC71
9
Flash memory
IC702
EEPROM
IC720
DSP
IC37
CODEC IC
IC4
TEST/SPKR
AOUT1~5
Divider
IC31
Flash memory
IC17
RS-232C
IC705
SDRAM
IC704,707
SRAM
IC700
Dsub25
CN58
Option
board
SW
Q700
Q702
Beat shift
X701
32.768kHz
X700
25.8048MHz
RF
control
MPU
IC34
RTC IC
IC701
SW
Q4
Q5
Beat shift
X1
14.7456MHz
SW
Q704,Q705
Beat
shift
X702
25MHz
SW
Q10,Q12
Beat
shift
X2
16.515072MHz
Modem
control
MPU
IC325
RX DSP
IC323
Flash memory
IC314
FRAME
IC302
TX_Vocoder
DSP
IC324
Buffer
IC313
PLL IC
IC315
CODEC IC
IC30
9
VCXO
12.288MHz
X300
SW
Q307
Q308
Beat shift
X301
14.7456MHz
1
9
.2MHz
OCXO control
Backup
BA300
UART
UART
Shift register IC
IC22
Shift register IC
IC1
SR_CLK
SR_DATA
SR_CLK
SR_DATA
STB
Shift register circuit (Display part)
Refer to Fig. 24.
STB
STB1
Shift register
(TX unit)
STB_1
DATA
QS
Fig. 22 Control circuit
Summary of Contents for NEXEDGE NXR-901
Page 154: ...1 E CN300 RX_IF_VN ...