BrightSign XD230 Hardware - Manual (Page 20)

BrightSign XD230, XD1030, XD1230
17
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 seven voltage levels present in the player: 12V, 5V, 3.3V, 2.5V, 1.8V, 1.5V, and 1V.
Reset
BrightSign XD players have a Low Voltage Reset circuit. This circuit will hold the RESET_L signal low until a valid 3.3V
power source is present.
BCM7421 CPU
BrightSign XD players utilize a BCM7421 Multimedia CPU. This CPU runs on 3.3V, 2.5V, and 1V and runs from a 27MHz
oscillator. The CPU is reset by the RESET_L signal from the low voltage reset circuit going into the RESET_IN pin on the
CPU. When the RESET_IN pin goes from low to high, the BCM7421 will boot from the NAND flash.
Built-in Flash
The boot code in the BCM7421 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 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.
SDRAM
BrightSign XD players each contain four DDR SDRAM devices. When the BCM7421 boots, it will copy the code from the
NAND flash device into the SDRAM and then execute the code from the SDRAM. The SDRAM runs at a clock rate of
800MHz, with a data rate of 1600MHz.