®
DEVICE
SPECIFICATION
PORT BYPASS CIRCUIT FOR FIBRE CHANNEL AND GIGABIT ETHERNET
PORT BYPASS CIRCUIT FOR FIBRE CHANNEL AND GIGABIT ETHERNET
S2057
S2057
FEATURES
• Supports ANSI X3T11 1.0625 Gbps FCALdisk
attach
• ANSI x3T11 Fibre Channel Compatible
• IEEE 802.3z Gigabit Ethernet Compatible
• 1250 Mbps (Gigabit Ethernet) operation
• Fully differential for minimum deterministic
jitter accumulation (10 ps nominal)
• TTL Bypass Select
• High speed LVPECL I/O
• 0.2 W Typical power dissipation
• 3.3 V power supply
• 20-pin TSSOP
devices in the loop. Normal mode is enabled by setting
the SEL pin ACTIVE, which includes the disk in the loop
via the DDI/DDO ports. When the disk drive is either
absent or non-functional, Bypass mode is selected by
setting the SEL pin INACTIVE. This routes data directly
from IN to OUT, bypassing the disk ports. Direct attach
Fibre Channel Disk Drives have an “LRC Interlock”
signal designed to directly control the select function.
Table 1 is a truth table describing the data flow through
the S2057.
Jitter Performance
The primary AC parameter of importance is determinis-
tic jitter accumulation (data eye degradation) inserted
by the port bypass circuit. The S2057 utilizes high
bandwidth, low skew differential circuitry to provide
symmetric rise and fall times and excellent noise immu-
nity. This results in a nominal deterministic jitter accu-
mulation of
±10
ps.
For arrays of disk drives greater than 4, it is recom-
mended that the S2057 be cascaded with the S2058
(Port Bypass with repeater) in a ratio of 4:1 to perform
clock and data retiming. This insures optimal jitter
performance for the disk array system.
GENERAL DESCRIPTION
The S2057 is a single channel Port Bypass Circuit
(PBC), designed to minimize jitter accumulation by
providing a high bandwidth fully differential data path.
Primary application is in Fibre Channel Arbitrated Loop
(FC-AL) disk arrays to allow hot swapping of FC-AL
drives. The S2057 is designed to support 1.0625 Gbps
and 1.25 Gbps data rates.
The S2057 is a high speed 2:1 multiplexer with 2 modes
of operation: Normal and Bypass. A block diagram is
shown in Figure 1, and a system diagram showing the
S2057 in a single loop of a disk array is shown in Figure 2.
A disk drive connects on the Disk Drive input and output
ports (DDIP/N, DDOP/N), while the INP/N and OUTP/
N ports connect to the upstream and downstream
Table 1. Truth Table
SEL1
0
1
OUT
IN
DDI
DDO
IN
IN
Figure 1. S2057 Block Diagram
DDO P/N
DDI P/N
SEL
1
IN P/N
0
PBC
OUT P/N
August 8, 2000 / Revision C
1
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
