FIN24C_06 Datasheet, PDF (6/25 Pages) Fairchild Semiconductor – uSerDes™Low-Voltage 24-Bit Bi-Directional Serializer/Deserializer

4-Bit Control Mode
When operating in 4-bit control mode, the master device
must be configured as MODE 2 (S2 = 1, S1 = 0) and the
slave device must be configured as MODE 1 (S2 = 0, S1
= 1). When operating in this mode, 24 data and control
bits can be sent from the master to the slave and 20 data
bits can be sent from the slave to the master. Unidirec-
tional control signals should be connected to DP[21:24].
2-Bit Control Mode
When operating in 2-bit control mode, both devices must
be configured in MODE 3 (S2 = S1 = “1”). In this mode,
22 bits can be sent in either direction. When operating in
a 2-bit control mode, serialized bits 21 and 22 appear on
outputs 23 and 24 of the deserializer.
Power-Down Mode: (Mode 0)
Mode 0 is used for powering down and resetting the
device. When both of the mode signals are driven to a
LOW state, the PLL and references are disabled, differ-
ential input buffers are shut off, differential output buffers
are placed into a HIGH-impedance state, LVCMOS out-
puts are placed into a HIGH-impedance state, LVCMOS
inputs are driven to a valid level internally, and all inter-
nal circuitry is reset. The loss of CKREF state is also
enabled to ensure that the PLL only powers up if there is
a valid CKREF signal.
In a typical application, the device only changes between
the power-down mode and the selected mode of opera-
tion. This allows for system-level power-down functional-
ity to be implemented via a single wire for a SerDes pair.
The S1 and S2 selection signals that have their operat-
ing mode driven to a “logic 0” should be hardwired to
GND. The S1 and S2 signals that have their operating
mode driven to a “logic 1” should be connected to a
system level power-down signal.
©2005 Fairchild Semiconductor Corporation
FIN24C Rev. 1.0.2
6
www.fairchildsemi.com