© 2006 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FIN12AC Rev. 1.1.2

7

LVCMOS Data I/O

The LVCMOS input buffers have a nominal threshold

operational when the device is operating as a serializer.

When the device is operating as a deserializer, the inputs

are gated off to conserve power.

The LVCMOS 3-STATE output buffers are rated for a

source / sink current of 2mA at 1.8V. The outputs are

active when the DIRI signal is asserted LOW. When the

DIRI signal is asserted HIGH, the bi-directional LVCMOS

I/Os are in HIGH-Z state. Under purely capacitive load

Figure 3.

LVCMOS I/O

Application Mode Diagrams

Modes 1, 2, 3: Unidirectional Data Transfer

Figure 4. Simplified Block Diagram for Unidirectional Serializer and Deserializer

Figure 4. shows basic operation when a pair of µSerDes is configured in an unidirectional operation mode.

Master Operation:

1. During power-up, the device is configured as a

serializer based on the value of the DIRI signal.

2. The device accepts CKREF_M word clock and gen-

erates a bit clock, which is sent to the slave device

through the CKSO port.

3. The device receives parallel data on the rising edge

of STROBE_M.

4. The device generates and transmits serialized data

on the DS signals, which is source synchronous with

CKSO.

5. The device generates an embedded word clock for

each strobe signal.

Slave Operation:

1. The device is configured as a deserializer at power-

up based on the value of the DIRI signal.

2. The device accepts the bit clock on CKSI.

3. The device deserializes the DS data stream using the

CKSI input clock.

4. The device writes parallel data onto the DP_S port

and generates the CKP_S only when a valid data

word occurs.

From

Deserializer

To

Serializer

From

Control

DP[n]

+

–

+

–

+

–

+

–

CKREF_M

CKSO

CKSI

CKP_S

DP[1:12]_S

Serializer

Control

BIT CK

Gen.

PLL

Master Device Operating as a Serializer

DIR = “1”

Slave Device Operating as a Deserializer

DIR = “0”

Deserializer

Control

Work CK

Gen

Serializer

Deserializer

DS

STROBE_M

DP[1:12]_M