BrightSign HD600 Hardware Guide - Manual (Page 12)

BrightSign HD600
This information applies to a product under development. Its characteristics and specifications are subject to change without notice. Roku assumes no
obligation regarding future manufacturing unless otherwise agreed to in writing.
www.rokulabs.com © Roku 2006
Theory of operation
Power Supply
The HD600 has a four voltages present. These are 5V, 3.3V, 2.5V, and 1.2V. 5V comes in from the
power connector and is used directly for USB, the video filter chip, and the optical SPDIF chip. 3.3V is
created from 5V by a AMC2596-ADJDDF switching regulator. Similar regulators are used to create 2.5V
for the DDR SDRAM, and 1.2V for the PNX1500 core voltage.
Reset
The HD600 has a Low Voltage Reset circuit made up of a ADM809SART. This circuit will hold the
RESET_L signal low until a valid 3.3V power is present.
PNX1500 CPU
The HD600 has a Philips PNX1500 Multimedia CPU in it. This CPU runs on 3.3V, 2.5V, and 1.2V. The
PNX1500 runs from a 27MHz oscillator. The PNX1500 is reset by the signal RESET_L from the low
voltage reset circuit going into the POR_IN_N pin on the PNX1500. When the POR_IN_N pin goes from
low to high, then the PNX1500 will look at the bootstrap pins GPIO0 and GPIO1, which are both pulled
low on the PNX1500. This forces the PNX1500 to boot from IIC serial flash.
Built in Flash
The HD600 contains two flash devices. One of the devices is denoted to be the IIC BOOT flash. This
flash is write protected from the factory and it contains the MAC address for the 10/100 Ethernet chip, as
well as the boot code and the SRB bytes. The boot code in the IIC serial flash instructs the PNX1500 to
continue the boot process by reading additional code from the on board RUN MODE NOR flash. This
flash can be updated in the field, either from on the flash slots or 10/100 Ethernet. Part of the RUN
MODE flash is also used to hold non-volatile parameters. The contents of the boot flash is copied into the
SDRAM, then the PNX1500 jumps to the boot code.
SDRAM
The HD600 contains two DDR SDRAM devices. When the PNX1500 boots, it will copy the code from
the NOR flash device into SDRAM, and then execute the code from SDRAM.
Serial Port
The HD600 uses two GPIO lines to communicate with the RS232 level shifter. GPIO58 is the RXD line,
and GPIO0 is the txd line. The MAX3221 creates valid RS232 voltage levels for the transmit pin by using
a capacitive voltage switcher. The TXD pin on the MAX3221 is disabled until a valid RS232 voltage is
detected on the RXD pin.