REF CLOCK
CLOCK
Tx
ENCODED DATA
CLOCK
SERIAL LINK
Rx
ENCODED DATA
ENCODED DATA
Rx
CLOCK
SERIAL LINK
Tx
ENCODED DATA
CLOCK
REF CLOCK
Figure 1. Point-to-Point Data Link.
-COMGEN
EWRAP
TS2
TS1
± SI
DATA BYTE 0
Tx [00:09]
DATA BYTE 1
Tx [10:19]
10
TTL INTERFACE
AND
INPUT LATCH
10
20
FRAME
MULTIPLEXER
I/O
SELECT
CABLE
DRIVERS
2
± LOUT
2
± SO
2
TBC
PLL/CLOCK
GENERATOR
INTERNAL
CLOCKS
LASER
DRIVER
± LZOUT
LASER
CONTROLS
-LZON
PPSEL
Figure 2. HDMP-1512 (Tx) Block Diagram.
Transmitter Operation
The block diagram of the HDMP-
1512 transmitter is shown in
Figure 2. The basic functions of
the transmitter chip are the TTL
Interface and Input Latch, Frame
Multiplexing, Input/Output
selection, cable drivers, Laser
Driver, and monolithic Phase
Locked loop clock generator. The
actual operation of each function
changes slightly, according to the
desired configuration and option
settings. Figures 18 and 19 show
schematically how to terminate
each pin on the HDMP-1512
when used in systems incorporat-
ing either copper or fiber media.
There are two main modes of
operation for the transmitter
chip, both are based on the
selected baud rate. The baud rate
is controlled by the appropriate
setting of the SPDSEL pin, #67.
When this pin is set low, the
transmitter operates at a serial
rate of 531.25 Mbaud. When pin
#67 is set high the transmitter
operates at a serial rate of 1062.5
Mbaud. As such, the two main
modes of operation are the
531.25 Mbaud mode and the
1062.5 Mbaud mode.
The transmitter does not encode
the applied data. It assumes the
SPDSEL
data is pre-encoded using the
8B/10B encoding scheme as
defined in ANSI X3.230-1994.
The TTL input interface receives
data at the standard TTL levels
specified in the dc Electrical
Specification table. The internal
phase locked loop (PLL) locks to
the transmit byte clock, TBC.
TBC is supplied to the transmitter
chip by the sending system. TBC
should be a 53.125 MHz clock
(± 100 ppm) as defined in
X3.230-1994. Once the PLL has
locked to TBC, all the clocks used
by the transmitter are generated
by the internal clock generator.
FAULT
657
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
