Usb Controller - Bose Companion 5 Service Manual

USB Controller

USB Controller
USB Controller
The TAS1020B (U6000) micro-controller also serves as the master controller for the system. It manages the
USB interface to the host computer including the enumeration of the system capabilities to the host computer.
U6000 is responsible for managing the status of the USB interface, monitoring the MUTE\ signal from the remote
control, monitoring the status of the audio stream passing through the DSP, and enabling the Vraw, +10V, and
SENSOR power supplies.
USB Controller Oscillator and Clock Generation
All clocks for the system are generated by U6000. Crystal X6000 is driven by U6000 to generate a 6.0MHz
reference clock. This reference is internally multiplied by U6000 to generate its own 48MHz system clock as
well as the internal 24.576MHz master clock for the serial TDM audio path. This internal clock is divided to
produce a 12.288MHz bit clock and a 48kHz frame sync clock for the TDM audio path described later in this
document. A separate 24.576MHz clock is provided for driving the DSP. In order minimize jitter on the output of
the phase-locked loop, a filter for the PLL power supply is created with the components R6009, C61, and C6001.
The PLL dynamics are controlled by the compensation components C6002, C6003, and R6000.
USB Interface
The tolerance of the impedance into which the USB data signals D+, D- must be terminated is relatively tight.
Components R8001, R8001, C8000 and C8001 provide the proper matching to the internal impedance of the data
transmitters of U6000. R8002 provides the necessary pull up to the D+ line in order to signal to the host that the
Companion 5 is present and is a full-speed device. The resistor divider R6011 and R6013 permits U6000 to
sense the presence of the USB5V signal from the host. U6000 is required to remove the signal to R8002
whenever USB5V is not detected.
The signals BADDATA at U6000.31 and USBINT\ at U6000.30 are used to transmit key USB status information
to the DSP controller. When the USB link to the host computer is performing normally, no activity is present on
these signals.
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