FIBRE CHANNEL/GIGABIT ETHERNET TRANSCEIVER
Parallel Output Clock Rate and Data Stretching
The S2070 supports both full rate and half rate out-
puts, selected via the RATEN input. Table 4 shows
the operating rate scenarios. When RATEN is INAC-
TIVE, a data clock is provided on RBC1 at the data
rate. Data should be clocked on the rising edge of
RBC1. When RATEN is ACTIVE the device is in full
rate mode, and complementary TTL clocks are pro-
vided on the RBC0 and RBC1 outputs at 1/2 the
data rate as required by the Fibre Channel standard.
Data is clocked on the rising edges of both RBC0
and RBC1. See Figures 9 and 10.
S2070
OTHER OPERATING MODES
Loopback Mode
The S2070 supports internal loopback mode in
which the serial data from the transmitter replaces
external serial data. The loopback function is en-
abled when the loopback enable signal, EWRAP, is
set ACTIVE.
The loopback mode provides the ability to perform
system diagnostics and to perform off-line testing of
the interface to guarantee the integrity of the serial
channel before enabling the transmission medium.
Figure 3 shows the basic loopback operation.
Table 4. Operating Rates
RATEN
0
0
1
1
Serial Input
Rate (Gbps)
1.25
1.0625
0.625
0.53125
RBC0
(MHz)
62.5
53.125
N/A
N/A
RCB1
(MHz)
62.5
53.125
62.5
53.125
Parallel
Output Rate
(Mbps)
125
106.25
62.5
53.125
Figure 3. Loopback Operation
output
disabled
CSU
Fibre Channel and Gigabit Ethernet standards re-
quire that the COMMA sync character appears on
the rising edge of the RBC1 signal. In full rate mode
the phase of the data is adjusted such that this re-
quirement is met. No alignment is necessary when
the S2070 is operating in half rate mode (RATEN
INACTIVE) since the output clock frequency is equal
to the parallel word rate.
In Fibre Channel and Gigabit Ethernet applications it
is illegal for multiple consecutive COMMA characters
to be generated. However, multiple consecutive
COMMA characters can occur in serial backplane
applications. The S2070 is able to operate properly
when multiple consecutive COMMA characters are
received: after the first COMMA is detected and
aligned, the RBC0/RBC1 clock operates without
glitches or loss of cycles. Additionally, COM_DET
stays high while multiple COMMAs are being output.
CRU
Receive Latency
The average receive latency is 8 byte times.
March 7, 2001 / Revision G
5
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
