Bose T1 ToneMatch, Руководство по обслуживанию

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DSP – Volume Controls
U518 is an A/D used to read volume knob settings. It also communicates with the DSP through
the primary SPI bus.
DSP – USB
Audio is passed between DSP and the TAS1020A USB chip with an I
2
S bus labeled USB_BICK,
USB_LRCLK, USB_SDIN1 and USB_SDOUT1.
Control of the TAS12020A is accomplished by bit-banging two flag pins (FLAG 2 and FLAG 3)
of the DSP to create an I
2 C bus.
DSP – LCD
LCD control is done with the DSP’s secondary SPI bus accessed through the Digital Audio
Interface, labeled SPI_CLK_B and SPI_MOSI_B
Memory
Audio is written to and read from SRAM for effects including delay and reverb,
The multiplexed address/data lines from the DSP are fed to latches controlled by the ALE line to
address the SRAM. AD0-7 write and read data.
Encoders, Buttons, Channel and Master Volume controls
In order to read the many inputs required, the encoders and button outputs are applied to
latches U511-14, which are polled by the DSP.
Address lines A21-23 are decoded in U509 to provide 8 control lines used as latch enables,
latch output controls, and a chip select for the SRAM. The Latch output controls of U509 are
NOR’d with the read enable to provide the appropriate signals for the latches.
LED Control and misc DSP outputs
Other DSP outputs are created by latching the A/D lines into U516-518. The latch enables are
provided by NOR-ing the Latch enable outputs of U509 with the write enable pin.
Button backlight LEDs are kept on at a low intensity level by 30K resistors that always allow a
small amount of current through the LED (e.g. R327 for LED 9). When the button is selected,
and the DSP wishes to light the button more brightly, the 30K is bypassed by, for example, Q3
and Q21, in order to turn the LED on fully and highlight the button state.
Theory of Operation