beaglebone-black - Flipbook - Page 53
BeagleBone Black
the ROM Code does not check the image size. The only drawback is that the image will cross the subsequent
image boundary. The raw mode is detected by reading sectors #0, #256, #512, #768. The content of these
sectors is then veri昀椀ed for presence of a TOC structure. In the case of a GP Device, a Con昀椀guration Header
(CH)*must* be located in the 昀椀rst sector followed by a GP header. The CH might be void (only containing a
CHSETTINGS item for which the Valid 昀椀eld is zero).
The ROM only supports the 4-bit mode. After the initial boot, the switch can be made to 8-bit mode for increasing
the overall performance of the eMMC interface.
6.2.13
Board ID EEPROM
The BeagleBone is equipped with a single 32Kbit(4KB) 24LC32AT-I/OT EEPROM to allow the SW to identify the
board. Table 7 below de昀椀ned the contents of the EEPROM.
Table 6.4: EEPROM Contents
Name
Size (bytes)
Contents
Header
Board Name
Version
4
8
4
Serial Number
12
Con昀椀guration Option
RSVD
RSVD
RSVD
Available
32
0xAA, 0x55, 0x33, EE
Name for board in ASCII: A335BNLT
Hardware version code for board in ASCII: 00A3 for Rev A3, 00A4
for Rev A4, 00A5 for Rev A5, 00A6 for Rev A6,00B0 for Rev B,
and 00C0 for Rev C.
Serial number of the board. This is a 12 character string which is:
WWYY4P16nnnn where, WW = 2 digit week of the year of production YY = 2 digit year of production BBBK = BeagleBone Black nnnn
= incrementing board number
Codes to show the con昀椀guration setup on this board. All FF
6
6
6
4018
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
Available space for other non-volatile codes/data
Fig. 6.17: EEPROM Design Rev A5
The EEPROM is accessed by the processor using the I2C 0 bus. The WP pin is enabled by default. By grounding
the test point, the write protection is removed.
The 昀椀rst 48 locations should not be written to if you choose to use the extras storage space in the EEPROM for
other purposes. If you do, it could prevent the board from booting properly as the SW uses this information to
determine how to set up the board.
48
Chapter 6. Detailed Hardware Design
