78P2351R 155Mbps NRZ to CMI Converter
PIN DESCRIPTION (continued)
CONTROL PINS
NAME
PIN
TYPE DESCRIPTION
Loopback Selection:
Low: Normal operation
Float: Remote Loopback Enable: Recovered receive data and clock are
10
CIT
CIT
LPBK
looped back to the transmitter for retransmission.
High: Local Loopback Enable: The serial transmit data is looped back and
used as the input to the receiver.
Clock Mode Selection:
Low: Reserved
Float: Reference clock is synchronous to transmit data. Clock is recovered
9
CKMODE
with a CDR and data is passed through a FIFO
High: Reference clock is plesiochronous to transmit data. Clock is
recovered with a CDR and the FIFO is bypassed
Advanced Tx Control 1:
Low: Enables fixed LVPECL equalizer at the transmit inputs SIDP/N (for
FR4 trace lengths up to 1.5m).
Float: Normal operation
56
1
CIT
CIT
TXOUT1
TXOUT0
High: Adds 2% positive peaking on leading edge (for bandwidth limiting
components between LIU and coax connector)
Advanced Tx Control 0:
Low: Nominal amplitude
Float: 5% amplitude boost
High: 10% amplitude boost
Transmitter Power Down:
When high, powers down the transmitter.
8
CID
CID
TXPD
SPSL
Serial Port Selection:
When high, chip is SW controlled through the serial port.
32
Reference Clock Frequency Selection:
Selects the reference frequency that is supplied at the CKREFP/N pins. Its level
is read in at power-up or on the rising edge of a reset signal at the PORB pin.
34
CIT
CKSL
Low: 19.44MHz
Float: 77.76MHz
High: 155.52MHz
13