XRS10L210 Datasheet, PDF (11/37 Pages) Exar Corporation – SERIAL ATA II: PORT SELECTOR

EXSTOR - 1 XRS10L210
REV. 1.04
SERIAL ATA II: PORT SELECTOR
3.2 Power Down Modes
Each Serial ATA link within the XRS10L210 features independent support for 3 power modes via MDIO
interface, as follows:
• Active: All parts of the link are active. All power-down signals are de-asserted.
• Partial: In partial mode, the input and output pipelines are shut down, but the PLL and the OOB generation
circuits are active.
• Slumber: In slumber mode, the PLL is also shut down, saving additional power but adding latency on exit.
3.3 Speed Negotiation
The XRS10L210 will automatically perform speed negotiation with the host and devices in order to verify
whether the second generation Serial ATA 3.0 Gbps data rate is available or whether the system will need to
fall back upon the first generation Serial ATA 1.5 Gbps data rate. Speed negotiation is performed on an
independent basis by each of the dual-channel macros. Speed negotiation is done independently on all host
and device ports by default. MDIO configuration can request a common negotiated speed on the host and
device ports if such a speed exists. To perform speed negotiation with a downstream device, the XRS10L210
will first perform a COMRESET/COMINIT handshake with the device and then performs a calibrate/
COMWAKE handshake. Following receipt of the device COMWAKE signal, the XRS10L210 will continually
send out a D10.2 signal while awaiting receipt of the device ALIGN primitive. Depending on the speed of the
ALIGN primitive, the XRS10L210 will be able to determine the PHY generation of the device, and provide the
appropriate 1.5 Gbps or 3.0 Gbps ALIGN primitive in return to the device, thus completing speed negotiation.
This process is outlined in Figure 8.
FIGURE 8. SERIAL ATA SPEED NEGOTIATION
For speed negotiation with an upstream host, after the COMRESET/COMINIT and COMWAKE handshake is
complete, the XRS10L210 will initially send out an ALIGN primitive at the 2nd generation 3.0 Gbps data rate. If
no confirming 3.0 Gbps ALIGN primitive is received from the host, the XRS10L210 will then step down and
attempt negotiation at the lower 1.5 Gbps data rate.
3.4 Port selector Implementation
The XRS10L210 provides full support for the Serial ATA II Port Selector specification. A Serial ATA Port
Selector is a mechanism that allows two different host ports to connect to the same device in order to create a
redundant path to that device. Only one host connection to the device is active at a time.
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