S2070 datasheet(5/20 Pages) AMCC

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S2070

FIBRE CHANNEL/GIGABIT ETHERNET TRANSCEIVER

March 7, 2001 / Revision G

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.

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Table 4. Operating Rates

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.

Receive Latency

The average receive latency is 8 byte times.

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.

output

disabled

CRU

CSU

Figure 3. Loopback Operation

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