TS-5700
CIRC U IT D ES CRI PTI O N
•
Digital U n it
The digita l unit consists of a D S P (IC507:
ADSP2181 KS-115), an EPROM (IC512: AM27C010-
120DC), a clock dividing logic (IC508: TC74HC4040AF,
IC511: TC7S04F), and CODEC (IC504: AK4506-VS),
which interfaces with the analog section.
The DSP is a 16-bit fixed-decimal DSP. It operates
with the 12.288MHz clock, but the internal clock is
24.576MHz. The internal clock is output from pin 22
(C LKOUT) of the DSP to the clock dividing logic. The
DSP IDMA (Internal Direct Memory Access) function
is used to transfer commands between the DSP and
microcomputer.
The clock dividing logic supplies 3072kHz, 384kHz,
and 12kHz to the CODEC using clocks from the DSP.
It also supplies the same clock to the DSP to synchro
nize with the CODEC.
The CODEC is a 16-bit
�l:
CODEC for audio equip
ment. There are two channels: R and L. The R chan
nel is used for the microphone input signal and the L
channel is used for the receive signal. The CODEC
converts analog signals to digital signals or digital sig
nals to analog signals based on the clock from the
clock dividing logic with a 12kHz sampling frequency.
• Flow of Transm it/Receive Sig n als
The flow of transmit/receive signals is explained
below, together with the analog and digital units.
The flow of receive signals is explained first The
receive signal input from pin 6 (DET) of CN502 is am
plified by IC503: NJM21 OOM. If a strong signal is in
put to DET, its amplitude is limited to prevent entering
of signals which exceed the input range into the
CODEC (IC504: AK4506-VS). It is then converted to
digital data by the CODEC with the 12kHz sampling
frequency. This data is transferred from the CODEC
to the DSP serial ly, and operated by the DSP.
The digital data processed by the DSP is sent from
the DSP to the CODEC serially and converted to an
analog signal . The signal passes through the three
degree low-pass filter IC505 and IC506: NJM21 OOM
to eliminate alias components. The resulting signal is
output from pin 1 (AF) of W501, amplified by the AF
amplifier (IC8: LA4446) in the TX-RX unit, and output
to the speaker and headphone.
The flow of transmit signals is explained below. If
the mode is S SB, FM, or AM, the signal from the mi
crophone is input The signal enters through CN503.
The signa l is amp l ified b y amplifier IC501:
NJM21 OOM, and goes to the analog switch (IC501:
BU4066BCFV). The analog switch is used to switch
between the microphone signal, the signal from the
DRU, and packet signal. The signal passing through
the ana log switch is ampl ified by amplifier IC503:
NJM2100M. If there is a strong signal, the amplitude
is limited so that the signal exceeding the input range
does not enter the CODEC. The COD EC then con
verts it to digital data with a 12kHz sampling fre
quency. The data is transferred from the CODEC to
the DSP to carry out operations.
Digital data operated by the DSP is transferred from
the DSP to the CODEC to convert it to an analog sig
nal. The signal passes through the three-degree low
pass filter IC505: NJM21 OOM to eliminate alias com
ponents. The signal is output pin 4 (MOD/ANO) of
CN502 to the TX-RX unit.
•
Sidetone Sig n al Flow
When the electronic keyer is pressed, the sidetone
is output. The sidetone is processed by the DSP.
Sidetone data, which is generated by the DSP, is
added with digital data of the receive signal and is out
put to the speaker or headphone in the same process
as the receive signal.
•
Beep Sig n al Flow
When pin 126 (BEEP) of the DSP goes high, the
DSP processes and outputs beep data in the same
process as the side tone. The DSP can set the fre
quency and volume of the beep produced with a com
mand.
• Digital Recording Unit (DRU) Recording and Playback
The DRU is controlled by the microcomputer. Dur
ing the DRU recording, the microphone signal ampli
fied by the amplifier (IC501: NJM21 OOM) is input to
the DRU and recorded. During DRU playback, the
playback signal is input to the CODEC by changing the
analog switch (IC502: BU4066BCFV). When the DSP
receives a " VOX ON and DRU playback " command
from the microcomputer, VOXS data in the DSP goes
high. When the microcomputer reads the data, it sets
the transceiver to transmit mode. This transmit opera
tion does not occur according to the playback sound
level of the DRU. Even if no sound is recorded, the
transceiver enters the transmit mode when a DRU
playback command arrives with VOX ON.
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