HDMP-1022 Datasheet, PDF (28/40 Pages) Agilent(Hewlett-Packard) – Low Cost Gigabit Rate Transmit/Receive Chip Set with TTL I/Os

Rx Operation Principles
The HDMP-1024 (Rx) is
monolithically implemented in a
high performance 25 GHz f_t
bipolar process. When properly
configured, the Rx can accept
20B/24B CIMT line code frames,
and then output parallel 16B/17B/
20B/21B Data Word or 14B/18B
Control Word. The Rx provides
the following functions for link
operation:
• Clock recovery
• Frame synchronization
• Data recovery
• Demultiplexing
• Frame decoding
• Frame error detection
• Link state control
Rx Encoding
Figure 5 shows a simplified block
diagram of the receiver. The data
path consists of an Input Select,
an Input Sampler, a Frame
Demultiplexer, a Control Field (C-
Field) Decoder, and a Data Field
(D-Field) Decoder. An on-chip
phase-locked loop (PLL) is used
to extract timing reference from
the serial input (DIN or LIN). The
PLL includes a Phase-Frequency
Detector, a Loop Filter, and a
variable-frequency oscillator
(VCO). All the RX internal clock
signals are generated from a
Clock Generator. The Clock
Generator can be driven either by
internal VCO or external signal,
TCLK, depending on the Clock
Select configuration.
Integrated on the chip is a Link-
Control State Machine for link
status monitoring and link
startup. Figure 13 shows the
details of the Input Select. The
Input Select chooses either
nominal serial data (DIN) or
loopback (LIN) signal for the
Input Sampler’s input. If loopback
enable (LOOPEN) is asserted, the
LIN input is selected. Also
included in the Input Selector is
cable equalization circuitry. When
coaxial cable is used as the
transmission media, by setting
EQEN=1 (enable equalization),
the equalization circuitry is in the
DIN signal path and can
compensate for high-frequency
cable loss.
Because the Data Field of the
CIMT line code can be either
16-bit or 20-bit wide, the width
selection for Rx is made by
setting the input pin M20SEL
(Figure 5). If M20SEL=1, then
the Rx is configured to accept
serial input with 20-bit data field,
i.e., 24 bits per frame. If
M20SEL = 0, 16-bit data field is
selected.
LOOPEN
EQEN
DIN
0
0
CABLE EQ
1
SIN
1
LIN
Figure 13. HDMP-1024 (Rx) Input Selector.
643