vsc880 Vitesse Semiconductor Corp, vsc880 Datasheet - Page 15

• Manufacturer Part Number: vsc880
• Description: High Performance 16x16 Serial Crosspoint Switch Semiconductor Corporation
• Manufacturer: Vitesse Semiconductor Corp

G52191-0, Rev 4.2
01/05/01
Data Sheet
VSC880
2.3 Receiver Operation
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).
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
0 0
Where:
B[1:0]00=Undefined,
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
The bit field C[0:15] is used to designate the output channels that are to be acted upon for a connection request
In Packet Mode, the receiver looks for connection request (CRQ) words from the transceiver. All data words and
01=Flow control channel,
10=Flow control channel,
11=Acknowledge
31 30 29 28 27 26 25
0 B B 1 0 1 0
1 0
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: [phone] • Email: [e-mail]
VITESSE
24
B
R
K
SEMICONDUCTOR CORPORATION
23 22 21 20
M M M M
00 01 02 03
Internet: www.vitesse.com
19 18 17 16
M M M M
04 05 06 07
------ Active Connections ------
15 14 13 12
M M M M
08 09 10 11
11 10 09 08
M M M M
12 13 14 15
High Performance 16x16
Serial Crosspoint Switch
07 06 05 04
D D D D
03 02 01 00
--Data--
03 02 01 00
1 0 1 0
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