VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
10-Bit Transceiver for Fibre
Channel and Gigabit Ethernet
VSC7123
Signal Detection
The receiver has an output, SIGDET, indicating, when HIGH, that the RX input contains a valid Fibre
Channel or Gigabit Ethernet signal. A combination of one analog and three digital checks are used to determine
if the incoming signal contains valid data. SIGDET is updated every four RCLKs. If during the current period,
all the four criteria are met, SIGDET will be HIGH during the next 4 RCLK period. If during the current period,
any of the four criteria is not met, SIGDET will be LOW during the next 4 RCLK period.
1) Analog transition detection is performed on the input to verify that the signal swings are of adequate
amplitude. The RX+/- input buffer contains a differential voltage comparator which will go HIGH if the
differential peak-to-peak amplitude is greater than 400mV or LOW if under 200mV. If the amplitude is
between 200mV and 400mV, the output is indeterminate.
2) Data on R(0:9) is monitored for all zeros (0000000000). If this pattern is encountered during the current
RCLK interval, the SIGDET output will go LOW during the next four RCLK interval.
3) Data on R(0:9) is monitored for all ones (1111111111). If this pattern is encountered during the current
RCLK interval, the SIGDET output will go LOW during the next four RCLK interval.
4) Data on R(0:9) is monitored for K28.5- (0011111010). Unlike previous patterns, the interval during which
a K28.5- must occur is 64K+24 10-bit characters in length. Valid Fibre Channel or Gigabit Ethernet data
will contain a K28.5- character during any period of this length. If a K28.5- is not detected during the
monitoring period, SIGDET will go LOW during the next period.
The behavior of SIGDET is affected by EWRAP and ENCDET as shown in Table 1.
Table 1: Signal Detect Behavior
Transition
Detect
All Zeros/
All Ones
K28.5
Presence
EWRAP
ENCDET
COMDET
Mode
0
0
1
1
0
1
0
1
Disabled
Enabled
Disabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Disabled
Disabled
Enabled
Disabled
Disabled
Disabled
Normal
SIGDET ignores commas
Rollback
Loopback
Note: COMDET, RCLK, RCLKN and R(0:9) are unaltered by SIGDET.
JTAG Access Port
A JTAG Access Port is provided to assist in board-level testing. Through this port, most pins can be
accessed or controlled and all TTL outputs can be tri-stated. A full description of the JTAG functions on this
device is available in “VSC7123/VSC7133 JTAG Access Port Functionality.”
G52212-0, Rev 4.3
03/25//01
Page 5
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
