capacitor on pin LZTC (# 27) will
begin to discharge. After
approximately 2 msec, the
voltage on LZTC falls to the fault
value and the error detector will
bring the FAULT pin (# 29) high
to alert the system. The error
detector will also hold the voltage
on LZMDF low, until a reset is
initiated.
The -LZON pin is used to disable
the laser driver under system
control or in conjunction with an
external open-fiber control (OFC)
chip. This pin is also used to
reset the error detector and
recharge the capacitor on pin
LZTC.
The LZPWRON pin, # 36, is used
to hold off dc power to the laser
driver until proper dc bias is
applied to the laser diode. When
LZPWRON goes high, the laser
driver is enabled, when it is low,
it is disabled. If not used, this pin
should be tied low.
Receiver Operation
The block diagram of the HDMP-
1514 receiver is shown in Figure
5. The functions included on the
receiver are a coaxial cable
equalizer, two independent loss
of light (LOL) detectors, an input
select function, monolithic phase
locked loop and clock recovery
circuits, a clock generator, frame
demultiplexer and comma
detector, power supply super-
visor, and output latch with TTL
drivers. Figures 20 and 21 show
schematically how to terminate
each pin on the HDMP-1514
when used in systems incorporat-
ing either copper or fiber media.
In the most basic sense, the
receiver accepts a serial electrical
data stream at 1062.5 Mbaud or
531.25 Mbaud and recovers the
8B/10B encoded parallel data and
clock that was applied to the
transmitter. Like the transmitter,
the receiver has several configu-
ration options which interrelate
-TCLKSEL
-LCK_REF
L_UNUSE
SPDSEL
EWRAP
according to the desired mode of
operation.
The two main modes of operation
for the receiver are based on the
desired signalling rate. The
signalling rate is controlled by
the proper setting of the SPDSEL
pin # 71. When this pin is set
low, the receiver operates at a
serial rate of 531.25 Mbaud.
When pin # 71 is set high, the
receiver operates at a serial rate
of 1062.5 Mbaud.
In a typical configuration, the
serial electrical data stream will
be applied to the
±
DI pins, # 19
and # 20 on the receiver. The
serial electrical data stream may
have been transmitted over a
fiber optic link or a copper cable
link (several variations of each
link type is possible). For use
with copper links, a selectable
cable equalizer is available at the
input. This equalizer can be
switched into or out of the data
DR_REF
LOL
DETECTORS
CLKIN
LOLA
LOLB
± DI
CABLE
EQUALIZER
INPUT
SELECT
PLL AND
CLOCK
SELECT
RBC0
CLOCK
GENERATOR
INTERNAL
CLOCKS
RBC1
-EQEN
± LIN
COM_DET
V
CC
_HS
SUPPLY
SUPERVISOR
FRAME
DEMUX
AND
COMMA
DETECT
20
OUTPUT
LATCH AND
TTL
INTERFACE
10
DATA BYTE 0
Rx [00:09]
DATA BYTE 1
Rx [10:19]
10
PS_CT
-POR
Figure 5. HDMP-1514 (Receiver) Block Diagram.
660
EN_CDET
PPSEL
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
