fin12a Fairchild Semiconductor, fin12a Datasheet - Page 8

• Manufacturer Part Number: fin12a
• Description: Fin12a Mserdes Low Voltage 12-bit Bi-directional Serializer/deserializer With Multiple Frequency Ranges Preliminary
• Manufacturer: Fairchild Semiconductor

www.fairchildsemi.com
PLL Circuitry
The CKREF input signal is used to provide a reference to
the PLL. The PLL will generate internal timing signals
capable of transferring data at 14 times the incoming
CKREF signal. The output of the PLL is a Bit Clock that is
used to serialize the data. The bit clock is also sent source
synchronously with the serial data stream.
There are two ways to disable the PLL. The PLL can be
disabled by entering the Mode 0 state. (S1
PLL will disable immediately upon detecting a LOW on
both the S1 and S2 signals. When any of the other modes
are entered by asserting either S1 or S2 HIGH and by pro-
viding a CKREF signal the PLL will power-up and goes
through a lock sequence. You must wait specified number
of clock cycles prior to capturing valid data into the parallel
port.
An alternate way of powering down the PLL is by stopping
the CKREF signal either HIGH or LOW. Internal circuitry
detects the lack of transitions and shuts the PLL and serial
I/O down. Internal references will not however be disabled
allowing for the PLL to power-up and re-lock in a lesser
number of clock cycles than when exiting Mode 0. When a
transition is seen on the CKREF signal the PLL will once
again be reactivated.
S2
0). The
8
Passing a Word Clock
For some applications it is desirable to pass a word clock
through the deserializer to the serializer and output it as a
reference clock for another device. (See Figure 11) This
can be done under the following conditions:
1. The application mode is unidirectional only.
2. The master word clock is generated on the same side
To implement pass through functionality on the deserial-
izer:
1. DIRI
2. CKREF
3. Word clock should be connected to the STROBE.
4. This will pass the STROBE signal out the CKSO port.
To implement pass through functionality on the serializer:
1. Connect CKSO of the deserializer to CKSI of the serial-
2. CKSI passes the signal to CKP
3. CKP must be connected to CKREF
If the word clock being passed through the serializer stops
then the serializer must be placed in the reset mode
(MODE 0) and restarted before the CKSI signal will again
pass through to CKP.
If CKREF of the deserializer is running then a high speed
bit clock will be passed across the flip instead of STROBE.
This bit clock will be used as the clock source by the serial-
izer provided that no CKREF signal exists on the serializer.
of the cable as the deserializer.
izer
LOW
LOW
Preliminary