PC87591L-N05 Datasheet, PDF (394/401 Pages) National Semiconductor (TI) – LPC Mobile Embedded Controller

C. Booter Program
The PC87591L-N05 Booter program resides in the 4K on-chip ROM.
The Booter has two main functions:
• On power-up, it performs all boot procedures and then passes control to the firmware (EC BIOS).
• If there is a problem with the firmware (EC BIOS), or if the user forces Recovery mode, the Booter enters Recovery
mode and allows debugging via JTAG or RS-232 debugging channels.
C.1 BOOT DATA
Header 1 resides at the address 1000₁₆ in the external flash and is defined as follows:
Offset Length
00-01
02-03
04-05
06
07
2
Signature
2
Bus Width
2 Address of Header 2
1
Action Flag
1
Config
.............
Header 2
Note: The first eight bytes are not included in the checksum count.
• Signature (two bytes at offset 0):
The signature can be one of the following:
— 49₁₆ in the lower byte and 4A₁₆ in the higher byte or 4A49₁₆ in little endian convention (Light signature),
— 49₁₆ in the lower byte and 4E₁₆ in the higher byte or 4E49₁₆ in little endian convention (Normal signature).
• Bus Width (one word at offset 2):
This byte instructs the Booter as follows:
Bit
Description
0-6 Reserved.
7 Bus width.
0: External flash device is in 8-bit data mode (byte wide)
1: External flash device is in 16-bit data mode (word wide)
8-15 Reserved.
.
• Address of Header 2: (1 word at offset 4)
The starting address of Header 2. This field stores the PC value of Header 2. Thus, its value is the address divided
by 2. Checksum counting begins at this address.
• Action Flag: (1 byte at offset 6)
Reserved.
• Config: (1 byte at offset 7)
This byte instructs the Booter as follows:
Bit
0 XOR Checksum.
0: Do not perform the XOR checksum
1: Perform the XOR checksum
Description
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