© VITESSE SEMICONDUCTOR CORPORATION

Page 3

1/17/00

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

VITESSE

SEMICONDUCTOR CORPORATION

10-bit Transceiver for Fibre

Channel and Gigabit Ethernet

Advance Product Information

VSC7133

G52187-0 Rev. 2.4

Deserializer

The recovered serial bit stream is converted into a 10-bit parallel output character. The VSC7133 provides

complementary TTL recovered clocks, RCLK and RCLKN, which are one twentieth of the serial baud rate. The

clocks are generated by dividing down the high-speed recovered clock which is phase locked to the serial data.

The serial data is retimed, deserialized and output on R(0:9). The parallel data will be captured by the adjoin-

ing protocol logic on the rising edges of RCLK and RCLKN.

If serial input data is not present, or does not meet the required baud rate, the VSC7133 will continue to

produce a recovered clock so that downstream logic may continue to function. The RCLK/RCLKN output fre-

quency under these circumstances will differ from its expected frequency by no more than +1%.

Word Alignment

The VSC7133 provides 7-bit comma character recognition and data word alignment. Word synchronization

is enabled by asserting ENCDET HIGH. When synchronization is enabled, the receiver examines the recovered

serial data for the presence of the “Comma” character. This pattern is “0011111XXX”, where the leading zero

corresponds to the first bit received. The comma sequence is not contained in any normal 8B/10B coded data

character or pair of adjacent characters. It occurs only within special characters, known as K28.1, K28.5 and

K28.7, which are defined for synchronization purposes. Improper alignment of the comma character is defined

as any of the following conditions:

1) The comma is not aligned within the 10-bit transmission character such that R(0..6) = “0011111”.

2) The comma straddles the boundary between two 10-bit transmission characters.

3) The comma is properly aligned but occurs in the received character presented during the rising edge of

RCLK rather than RCLKN.

When ENCDET is HIGH and an improperly aligned comma is encountered, the recovered clock is

stretched, never slivered, so that the comma character and recovered clocks are aligned properly to R(0:9). This

results in proper character and word alignment. When the parallel data alignment changes in response to a

improperly aligned comma pattern, some data which would have been presented on the parallel output port may

be lost. Also, the first Comma pattern may be lost or corrupted. Subsequent data will be output correctly and

properly aligned. When ENCDET is LOW, the current alignment of the serial data is maintained indefinitely,

regardless of data pattern.

On encountering a comma character, COMDET is driven HIGH.

The COMDET pulse is presented simul-

taneously with the comma character and has a duration equal to the data, or half of an RCLK period. The COM-

DET signal is timed such that it can be captured by the adjoining protocol logic on the rising edge of RCLKN.

Functional waveforms for synchronization are given in Figure 2 and Figure 3. Figure 2 shows the case when a

comma character is detected and no phase adjustment is necessary. It illustrates the position of the COMDET

pulse in relation to the comma character on R(0:9). Figure 3 shows the case where the K28.5 is detected, but it

is misaligned so a change in the output data alignment is required. Note that up to three characters prior to the

comma character may be corrupted by the realignment process.