LSx22 Theory of Operation

power supply there are five voltages present in the player 5v, 3 3v, 2 5v, 1 5v, and 1 2v the 3 3v level for the usb port is created from 12v using a switching regulator similar regulators are used to create the 2 5v level for the ddr sdram and the 1 2v level for the cpu core voltage bcm7208 cpu the ls322 and ls422 utilize a bcm7208 multimedia cpu 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 from either sd or usb 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 when the bcm7208 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 667mhz, with a data rate of 1333mhz audio outputs the ls322 and ls422 each have a single high quality audio dac device, which takes in digital audio signals from the cpu in i2s audio format the aud lrcin is the framing signal for the audio and runs at the frequency of the audio source (usually either 44 1khz or 48khz) the aud bitclk signal is typically 32 times higher than the aud lrcin the audio output is fed through an amplifier and sent directly to the audio output jack it can drive a 32ω load with a 2v rms signal on board switch the on board switch is connected to the gpio12, which is pulled low when the service (svc) button is pressed conversely, a pull up on the button normally sets the gpio12 to be pulled high reset switch / gpio button the on board switch is connected to the reset button pressing down the reset button will send a reset signal to the system software nand flash brightsign players have a built in nand flash all the code for the player is stored on the nand flash it may also be possible to store some content on the nand flash, which is connected directly to the bcm7208 ethernet the 10/100 base t ethernet is implemented on the ls322 and ls422 by directly interfacing with the bcm7208 the player has on board ethernet magnetics and termination for the rj 45 cable usb 2 0 the usb 2 0 high speed host controller is implemented internally in the bcm7208 soc chip the board utilizes over current protected switches that can be used to turn the power to usb devices on or off (or to detect over current situations)