BrightSign HD120, HD220, HD1020
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All information provided in this reference manual applies to products under development. The characteristics and specifications of these products are subject to
change without notice. BrightSign assumes no obligation regarding future manufacturing unless otherwise agreed to in writing. © BrightSign LLC, 2012
THEORY OF OPERATION
Power Supply
There are five voltages present in the player: 5 V, 3.3 V, 2.5 V, 1.5 V and 1.2 V. 5 V comes in from the power connector
and is used directly for the USB. 3.3 V is created from 5 V by a switching regulator. Similar regulators are used to create
2.5 V for the DDR SDRAM and 1.2 V for the CPU core voltage.
Reset
The HD120, HD220, and HD1020 players have a Low Voltage Reset circuit. This circuit will hold the RESET_L signal low
until a valid 3.3 V power source is present.
BCM7208 CPU
The HD120, HD220, and HD1020 players utilize a BCM7208 Multimedia CPU. This CPU runs on 3.3 V, 2.5 V, and 1.2 V
and runs from a 27 MHz oscillator. The CPU is reset by the RESET_L signal from the low voltage reset circuit going into
the RESET_IN pin on the BCM7208. When the RESET_in pin goes from low to high, the BCM7208 will boot from the
NAND flash.
Built-in Flash
The boot code in the BCM7208 instructs it to continue the boot process by reading additional code from the onboard
NAND flash, which can be updated in the field, either from on the flash slots or USB mass storage. Part of the NAND flash
is also used to hold non-volatile parameters. The contents of the boot flash are copied into the SDRAM. The CPU then
jumps to the boot code.
