Appendix B: Oob/Beacon Signaling; Oob Signaling In Sata - Xilinx Virtex-5 RocketIO GTP User Manual

R
OOB/Beacon Signaling
The GTP transceiver provides support for Out-of-Band (OOB) signaling to support
standards such as SATA and beaconing for PCI Express. OOB signaling mechanisms are
used to send low-speed signals between the transmitter and receiver when high-speed
serial data transmission is not active, typically when the link is in a power-down state or
has not been initialized.
OOB signaling uses non-differential transitions on the differential inputs of the receiver to
send information. To send an OOB signal, transmitters drive their serial differential output
pins to the same voltage, resulting in a reduced differential voltage between the pins.
When the absolute differential voltage drops below a preset threshold level, the receiver
detects the signal as an OOB signal.
Differential
"TX OOB/Beacon Signaling," page 119
provide details of the support for OOB signaling in the GTP transceiver TX and RX logic,
respectively. The remainder of this section summarizes the use of OOB signaling in SATA
and beaconing for PCI Express.

OOB Signaling in SATA

SATA uses OOB signals as part of its COMWAKE, COMINIT, and COMRESET sequences
as shown in
followed by an OOB signal (called an idle signal in SATA). The length of the idle defines
the type of COM sequence being received: COMWAKE sequences use 106.7 ns idles, and
COMINIT/COMRESET sequences use 320 ns idles. A COM sequence is valid when it is
received four times consecutively.
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
RXP
RXN
Voltage
Figure B-2. These sequences consist of a fixed length burst of non-OOB data
www.xilinx.com
Figure B-1 illustrates this concept.
OOB Signal
Figure B-1: OOB Signaling
and "RX OOB/Beacon Signaling," page 129
Appendix B
V+
V com
V-
2V+
OOBDETECT_THRESHOLD
2V-
UG196_B_01_092606
267