VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC880

High Performance 16x16

Serial Crosspoint Switch

G52191-0, Rev 4.2

Page 15

01/05/01

© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

Internet: www.vitesse.com

Where:

B[1:0]00=Undefined,

01=Flow control channel,

10=Flow control channel,

11=Acknowledge

BRK1=This is the CRQ word for the next packet. This bit is used to break the current connection.

M[0:15]Current outputs the transmitting channel is connected to

D[3:0] User defined data sent by transmitting port card

2.3 Receiver Operation

In Packet Mode, the receiver looks for connection request (CRQ) words from the transceiver. All data words and

IDLE words are passed on directly to the switch matrix. If BRK is HIGH, the current connection will be broken

before processing the new connection request word. When BRK is LOW, the switch does not break current

connections when making a new request. When AOA is HIGH, the switch will send an ACK only if the current

switch connections match the C[0:15] bit field. When AOA is LOW, an ACK is sent back to the transceiver when any

connection in the C[0:15] bit field is granted. In both cases, a response word is also returned to the transceiver from

the switch. The response word can be embedded into an IDLE word or CRQ word that is sent back to the transceiver.

If the transceiver makes a CRQ that requires a response (i.e., a multicast CRQ), the switch uses the flow control

channel to force an IDLE word into the receiving data stream by forcing the internal ready to receive (RTR) signal

low for one word clock (see the VSC870 data sheet).

The bit field C[0:15] is used to designate the output channels that are to be acted upon for a connection request

operation. To request an output to connect to, set the corresponding bit HIGH. Multiple bits can be set HIGH at the

same time for multicast. The sending port card can include 4 bits of data (D[3:0]) in the CRQ word that will be passed

on to the destination port card. Two example word sequences from the transceiver on the serial interface are shown in

the Figure 7. The two overhead bits (BB) are used for signaling on data words (see the VSC870 date sheet).

33 32

31 30 29 28 27 26 25

24

23 22 21 20

19 18 17 16

15 14 13 12

11 10 09 08

07 06 05 04

03 02 01 00

0 0

0 B B 1 0 1 0

1 0

B

R

M M M M

00 01 02 03

M M M M

04 05 06 07

M M M M

08 09 10 11

M M M M

12 13 14 15

D D D D

03 02 01 00

1 0 1 0

K

------ Active Connections ------

--Data--