Co. Ltd. Modem User Manual

CiM-550 IP Enabled Satellite Modem Rev. 2
Theory of Operation CD/CIM550.IOM
86
6.3.4 TRANSMIT AND RECEIVE CLOCKING
EXTERNAL TX CLOCK MODE
TX DATA
TX CLOCK
(TT)
TRANSMIT
DATA
INTERFACE
TX
FIFO
PLL
CIRCUIT
CLOCK
VCXO
DATA TO
MODULATOR
CIRCUIT
THE MODEM LOCKS ITS CLOCK CIRCUITS
TO THIS CLOCK COMING FROM THE
EXTERNALLY CONNECTED EQUIPMENT
INTERNAL TX CLOCK MODE
TX DATA
TX CLOCK
(TT)
INTERNAL
CLOCK
(ST)
TRANSMIT
DATA
INTERFACE
TX
FIFO
PLL
CIRCUIT
CLOCK
VCXO
DIRECT
DIGITAL
SNTHESIZER
14.4 MHz
TCXO
DATA TO
MODULATOR
CIRCUIT
THIS CLOCK IS USED AS THE SYNCHRONIZATION
SOURCE FOR THE EQUIPMENT ATTACHED
TO THE MODEM
LOOP-TIMED TX CLOCK MODE
TX=RX OR TX<>RX
TX DATA
TX CLOCK
(TT)
INTERNAL
CLOCK
(ST)
TRANSMIT
DATA
INTERFACE
TX
FIFO
PLL
CIRCUIT
CLOCK
VCXO
DIRECT
DIGITAL
SNTHESIZER
DATA TO
MODULATOR
CIRCUIT
THIS CLOCK IS USED AS THE SYNCHRONIZATION
SOURCE FOR THE EQUIPMENT ATTACHED
TO THE MODEM
PLL
CIRCUIT
CLOCK
VCXO
RX SYMBOL
CLOCK FROM
DEMOD
Figure 6-1. Tx Clock Modes