78P2351R
Serial 155M
NRZ to CMI Converter
Pulse Amplitude Adjustment
Contact TDK applications for information on user
programmable registers with up to 200mV of
programmable transmit gain.
TD +
Fixed
CDR
Eq.
TD -
CMI
ENDEC
Line-side
RD +
Adaptive
Eq.
CDR
Transmit Backplane Equalizer
RD -
An optional fixed LVPECL equalizer is integrated in
the transmit path for architectures that use LIUs on
active interface cards. The fixed equalizer can
compensate for up to 1.5m of trace and can be
enabled by the TXOUT1 pin or TXEQ bit as follows:
Figure 3: Remote (analog) Loopback
TD +
TD -
TXEQ bit
Tx Equalizer
TXOUT1 pin
Fixed
CDR
Eq.
Low
Float
1
0
Enabled
Disabled
CMI
ENDEC
Adaptive
CDR
Eq.
RD +
RD -
POWER-DOWN FUNCTION
Power-down control is provided to allow the
78P2351R to be shut off. Transmit and receive
power-down can be set independently through SW
Figure 4: Local (analog) Loopback
control.
Global power-down is achieved by
In SW mode only, a Full Remote (digital) Loopback
bit FLBK is also available in the Advanced Tx
Control register. This loopback exercises the entire
Rx and Tx paths of the 78P2351 including the Tx
clock recovery unit. As such, the user must enable
either Plesiochronous or Loop-timing transmit modes
to utilize the Full Remote (digital) Loopback.
powering down both the transmitter and receiver.
Note: the 4-wire serial port interface and
configuration registers are not affected by power-
down.
The transmitter can also be powered down using the
TXPD control pin. The CMI outputs are tri-stated
during transmit power-down for redundancy
applications.
The TXPD pin is active in both
TD +
TD -
Fixed
Eq.
CDR
hardware and software modes.
CMI
Line-side
LOOPBACK MODES
In SW mode, LLBK and RLBK bits in the Signal
Control register are provided to activate the local
and remote analog loopback modes respectively.
ENDEC
RD +
RD -
Adaptive
Eq.
CDR
In HW mode, the LPBK pin can be used to activate
local and remote analog loopback paths as shown in
the table below.
Figure 5: Remote (Digital) Loopback
LPBK pin Loopback Mode
Low
Normal operation
Remote (analog) Loopback:
Recovered receive clock and data
looped back directly to the transmit
driver. The CMI decoder and most of
transmit path is bypassed (including the
redundant Tx monitor output)
Float
Local (analog) Loopback:
High
Transmit clock and data looped back to
receiver at the analog media interface.
Page: 6 of 31
2006 Teridian Semiconductor Corporation
Rev. 2.1
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
