VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
High Performance Serial
Backplane Transceiver
VSC870
11XX0=Command word for receiving port card
D[15:0]Optional data payload:
Default=1010101010101010
IDLE Word from switch=Output(s) this port is connected to;
D[15] is equal to port 0, and D[0] is equal to port 15.
If C[4:0]=01000, D[3:0]=DLYEN/CCKIN value
1.2.4 Command Word Format on the Serial Data Lines
The command word format as seen at the serial output of the transceiver or switch chip is shown below. Two
overhead bits are added by the transceiver or switch to designate a command word (00) to the receiving switch chip or
transceiver. The serial data is transmitted with the MSB first. In Packet Mode, the IDLE word from the switch always
returns the current output connections for the port.
33 32
0 0
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
1 0 1 0
03 02 01 00
1 0 1 0
1 B B
1 0
C C C C C
04 03 02 01 00
D D D D
15 14 13 12
D D D D
11 10 09 08
D D D D
07 06 05 04
D D D D
03 02 01 00
-- Command --
-- Data --
Where:
B[1:0]00=Undefined (during normal operation) or alignment word
01=Flow control channel,
10=Flow control channel,
11=Acknowledge (from switch chip only) or link initialization reset or cell clock in cell mode
C[4:0]Command type:
00XXX=Link Control (00000=ALIGN word, 00111=IDLE word)
01XX0=Command word for transceiver (01000=set DLYEN/CCKIN value)
10XX0=Command word for switch
11XX0=Command word for receiving port card)
D[15:0]Optional data payload:
Default=1010101010101010
IDLE Word from switch=Output(s) this port is connected to;
D[15] is equal to port 0, and D[0] is equal to port 15.
If C[4:0]=01000, D[3:0]=DLYEN/CCKIN value
1.2.5 IDLE Words
IDLE words are the default word used on the serial channel when none of the other word types are present. In
most cases, these words are automatically generated by the transceiver or switch chip. In Packet Mode, IDLE words
are inserted between packets and the IDLE word from the switch always returns the current output connections for
the port that is receiving the IDLEs. If the user does not have data to send, IDLE words can be loaded into the parallel
interface, or the TXEN signal can be set LOW which forces the transceiver to send IDLEs to the switch chip. In cell
mode, IDLEs will be transmitted from the switch chip if the Force IDLE bit is set in the switch chip (see the VSC880
data sheet). See sections 2.0 and 3.0 for more details. IDLE words are also used to detect link error conditions. If the
transceiver detects and IDLE word, it uses a bit mask to verify the proper bit pattern within the word.
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
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