TCC76x
Specification Rev. 0.07
February 23, 2005
32-bit RISC Microprocessor for Digital Media Player
BOOTING PROCEDURE
Preliminary
20-3
20.3 USB Boot (BM == x1x)
This mode is mainly for firmware upgrade mode. In this mode, user can download a
program into internal SRAM and execute. The procedure of this mode is as follows.
i)
The TCC76x makes internal SRAM area starts from zero, and copies USB service
routine to internal SRAM area.
ii) It change control flow from boot ROM to internal SRAM where the USB service
routine just copied.
iii) It waits until USB connection is established.
iv) Once it is connected, host transfers first the parameter for USB loader routine
including start address, destination address, and the amount of data to be transferred.
v) The TCC76x starts communicating between a host PC with fixed amount of data
which is called as packet.
vi) At every successful reception of packet, it copies that where the destination address
pointed, and after all amount of data has been copied, it starts program where the start
address pointed.
Normally, the program downloaded is for writing user system firmware to non-volatile
memory like NOR or NAND flash.
To use USB boot, the clock frequency of XIN must be 12MHz. The internal PLL is used
to generate 48MHz of USB clock from XIN.
The following figure illustrates the sequence of USB boot mode described above.
Copy the packet to destination block
All amount of
Data ?
No
Yes
Jump to Start Address of USB loader
Mode Setting
Set PLL for USB operation
Set internal SRAM starts from zero
Copy USB service routine to SRAM
JUMP to SRAM (0x00000000)
Connection
Established ?
Yes
Receive the parameter for USB loader
Receive the packet
No
Figure 20.2 USB boot procedure
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