详细说明：

EM2874是禾瑞亚公司针对数字电视棒(DMB-TH)出的USB主控芯片.
EM2874 is an USB digital video capture device supporting two MPEG2 transport
stream interfaces. The device uses an embedded microcontroller 8051 to decode
USB requests and control various I/O's. Microcode is stored off chip and
downloaded to on-chip cache at power up. Transport streams are directly
transferred, bypassing the microcontroller. The chip aims for small package
and low pin count, therefore supports only serial form of transport streams
with 4 pins for each stream. One of the transport stream interface supports
encryption so the data sent through the USB port cannot be played
directly without being decrypted with the same key by the driver or the
application program. The chip supports both high bandwidth USB High
Speed mode and low bandwidth USB Full Speed mode. In order for the video
stream to fit in the limited bandwidth of USB Full Speed mode a transport
stream PID filter is built in to cut out unnecessary traffic on USB. To
facilitate a complete DTV solution, the chip supports two command serial buses
for communication with tuner, demodulator and microcode EEPROM. For added
value, an infrared protocol decoder is integrated on chip that supports NEC,
RC5 and RC6 remote control protocols. The chip also integrates an UART for
firmware debugging.
Features
- USB 2.0 and 1.1 compliant
- Embedded turbo 8051 microcontroller runs 2 to 4 clocks per instruction
- Support ISDB_T, DMB_T/H, DVB_T/H, ATSC, QAM, DVBS demodulators
- Dual transport stream input ports
- Receive serial form transport streams
- Transport stream PID filters allowing in packets of 15 PID's
- Null PID filter rejecting null packets
- Firmware may choose isochornous or bulk endpoints for transport streams
- Transport streams are DMA'ed to USB for max performance
- Encryption for transport stream data
- Many general I/O ports controlled by 8051
- May use general I/O port for LED
- Decode infrared remote control protocols NEC, RC5, and RC6
- UART port for microcode debugging
- Fully customizable microcode in external EEPROM, sized 4 KB or 8 KB.
- Customizable Vendor ID, Product ID, Vendor String, Product String
- 2 sets of 2-wire serial command bus to tuner, demodulator, and EEPROM
- USB suspend output to tuner and demodulator
- 0.18 micron, 1.8V core, 3.3V I/O CMOS process
- 48 pin QFN package