SLK2721

OC48+FEC/24/12/3 SONET/SDH MULTIRATE TRANSCEIVER

WITH ENHANCED JITTER TOLERANCE

SLLS532 − JUNE 2002

7

POST OFFICE BOX 655303

detailed description

The SLK2721 device is designed to support the OC-48/24/12/3 data rates. It also supports a higher data rate

that may be required for FEC support, up to 2.7 Gbps. The operating data speed can be configured through the

RSEL0 and RSEL1 pins as indicated in Table 1 for normal SONET rates. For FEC support, the clock and data

rates need to be scaled up as required. The highest data and clock rates supported are 675 Mbps and 675 MHz,

respectively.

Table 1. Data Rate Select

SERIAL DATA RATE

RSEL0

RSEL1

PARALLEL LVDS DATA RATE

TXCLK/RXCLK

OC-48: 2.488 Gbps

0

0

622.08 Mbps

622.08 MHz

OC-24: 1.244 Gbps

1

0

311.04 Mbps

311.04 MHz

OC-12: 622 Mbps

0

1

155.52 Mbps

155.52 MHz

OC-3: 155.52 Mbps

1

1

38.88 Mbps

38.88 MHz

The user can also enable the autorate detection circuitry through the AUTO_DETECT pin. The device

automatically detects the OC-N of the data line rate and generates two bits of output to indicate the data rate

to other devices in the system. When using AUTO_DETECT, RSEL0 and RSEL1 need to be set to 00 or be

unconnected.

Table 2. Data Rate Reporting Under Autorate Detection Mode

SERIAL DATA RATE

RATEOUT0

RATEOUT1

PARALLEL LVDS DATA RATE

TXCLK/RXCLK

OC-48: 2.488 Gbps

0

0

622.08 Mbps

622.08 MHz

OC-24: 1.244 Gbps

1

0

311.04 Mbps

311.04 MHz

OC-12: 622 Mbps

0

1

155.52 Mbps

155.52 MHz

OC-3: 155.52 Mbps

1

1

38.88 Mbps

38.88 MHz

The SLK2721 device has four operational modes controlled by two configuration pins. Table 3 lists these

operational modes. When the device is put in a certain mode, unused circuit blocks are powered down to

conserve system power.

While the transceiver mode, transmit only mode, and receive only mode are straightforward, the repeater mode

of operation is shown in Figure 4. The receive serial data is recovered by the extracted clock, and it is then sent

back out on the transmit serial outputs. The data eye is open both vertically and horizontally in this process. In

the repeater mode, the user can select to turn on the RX demultiplexer function through RX_MONITOR pin and

allow the parallel data to be presented. This feature enables the repeater device not only to repeat but also to

listen in.

Table 3. Operational Modes

MODE

CONFIG0

CONFIG1

DESCRIPTION

1

0

0

Full duplex transceiver mode

2

0

1

Transmit only mode

3

1

0

Receive only mode

4

1

1

Repeater mode

high-speed electrical interface

The high-speed serial I/O uses a PECL-compatible interface. The line could be directly coupled or ac-coupled.

Refer to Figures 10 and 11 for configuration details. As shown in the figures, an on-chip 100-

Ω termination

resistor is placed differentially at the receive end.