This is a small chunk of communication on the SCLK and SDIO pins of the
Avago ADNS-2051 optical mouse sensor.

Datasheet:
http://www.avagotech.com/docs/AV02-1364EN (PDF)
http://www.avagotech.com/pages/en/navigation_interface_devices/navigation_sensors/led-based_sensors/adns-2051/