xburst-tools/README

Pi is a Chinese device. 
We want port Openmoko to Pi, All free software

1. open the case

2. take off the cover of PCB
   then you will send the "GND" and "TXD"
   and th TP74 is the "RXD"
   you can get serial output from those pins 

3. you need a "RS-232 <--> TTL" converter to 
   get the correct output date

CPU Jz4740:

Jz4740 is a multimedia application processor targeted at mobile devices 
PMP. Incorporates the XBurst CPU core based on leading 
micro-architecture technology, this processor provides high integration, 
high performance and a low power consumption solution for embedded devices.

Boot up
The Jz4740 can be set to boot from NOR or NAND.
If booted from NAND, the CPU fetches the first page from NAND and uses the first 4 bytes on it to know how the NAND chip should be treated (16/8-bit bus, 2/3 row cycles).
After that it copies the first 8kB from NAND and copies it to the I-Cache for execution.

Ingenic Media Extension Instruction Set
According to the MXU User Guide, the XBurst processor supports additional instructions called the Ingenic Media Extension Instruction Set (they call it an SIMD instruction set).

Excerpt from the PDF:
Processors (such as the Jz4740) have 60 extra SIMD commands used for the optimization of multimedia codecs such as MPEG4, H264, VC-1, RMVB, ... and other multimedia decoder algorithms that can be optimized using the MXU.

Image Processing Unit
The Jz4740 also has an IPU which has the following features:

    * Video frame resize
    * Color space conversion: 420/444/422 YUV to RGB convert