12
LDM-144LR
Figure 2-1. LDM-144LR Block Diagram.
2.3.1 E
NCODER
M
ODULATOR
The Encoder Modulator receives data from the DTE and modulates it by
means of the partial-response modulation technique. The Encoder
Modulator can operate in one of the following modes:
• 4-wire full-duplex
• 4-wire half-duplex
2.3.2 M
ODULATION
T
IMING
This circuit supplies the transmit clock to the Encoder Modulator. Three
clock sources are available:
• The modem’s internal crystal oscillator, INT
• The DTE clock, EXT
• The receive signal recovered clock, RCV
Setting the transmit clock jumper (J1) determines the timing mode of the
LDM-144LR.
CTS
Delay
OSC
Power
Supply
Modulation
Timing
REM
COMMAND
GENERATOR
RTS
BERT
ERROR
Encoder
Modulation
REM
COMMAND
GENERATOR
V.54
Diagnostics
PATT
REM
RTS
CTS
TXC
EXT
CLK
TXD
REM
ANA
RXD
TXD
TXD
CNT/ON
DIG
Encoder
Modulation
Transmit
Filter
Selectable Level
Transmit Filter
Loopback
Timing
RLB
Command
Decoder
Decoder
Timing
Recovery
Carrier
Detect
DATA
RATE
Automatic
Equalizer
ANA
TX
TX
Selectable Level
Receiv Amplifier
DIG
LPBK
5
6
7
3
2
1
4
0
