vsc880 Vitesse Semiconductor Corp, vsc880 Datasheet - Page 19

• 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
3.4 Transmitter Operation
fabric. If the force IDLE register is set HIGH, IDLE words are transmitted. At the end of the cell clock period, bits
B[1:0] in all IDLE words are set to 11 to embed the cell clock marker. For data words, user defined overhead bits are
passed on to the destination as is.
3.5 Delaying The Cell Clock
the cell clock (CCLK) on the switch card, and the transmit cell clock (RTM/TCLK) on the port card. A cell clock
delay value can be programmed into the control register CDEL[3:0] to set the time the switch is configured after
receiving a cell clock. This adds 1-14 word clocks worth of delay between CCLK input to the switch chip and the cell
clock sent to the transceivers from the switch chip. In this way, the transmit cell clock (RTM/TCLK) on the
transceivers can be aligned to the cell clock at the switch chip (CCLK). For a typical system design where the
transceiver is less then 20” from the switch chip, the default value of 5 can be used. See Application Note 32 for more
details.
If out-of-band messaging is used between the port cards and the switch card, there will be a phase offset between
If CMODE is HIGH and the force IDLE register is set LOW, the transmitter sends data words from the switch
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High Performance 16x16
Serial Crosspoint Switch
Page 19