User manual

Table Of Contents
Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 184
UG585 (v1.11) September 27, 2016
Chapter 6: Boot and Configuration
Partition Memory: dividing flash memory into logical sections (partitions) with consideration for
bad blocks.
Bad Block Management
The BootROM manages bad blocks in the following ways:
It looks for a bad block table (BBT) in the last four blocks of the NAND flash device.
It supports a primary and secondary BBT with versioning allowing safe software updates.
If a BBT is not present, the BootROM scans the flash reading the out-of-band (OOB) information
to determine the locations of bad blocks.
The BootROM only performs read operations – it does not write to the flash.
While reading from NAND, the BootROM skips blocks that are marked as bad in the BBT, or in the
OOB information if a BBT does not exist.
For example: consider a flash device that has bad blocks located at blocks 1 and 3 (see Figure 6-6):
When programming the image into the flash device, blocks 1 and 3 must be skipped.
When reading, the BootROM reads the full user data from the good blocks as they are
encountered.
X-Ref Target - Figure 6-6
Figure 6-6: NAND Flash Device with Bad Blocks Example
8VHU'DWD
8*BFBB
8VHU,PDJH
%ORFN
8VHU'DWD
)ODVK'HYLFH
%ORFN
8VHU'DWD
%ORFN
8QXVHG
8QXVHG
8QXVHG
%ORFN
%ORFN
%ORFN
%ORFN
8QXVHG
%ORFN
8VHU'DWD
%ORFN
%ORFN
8VHU'DWD
%ORFN
8QXVHG
%ORFN
%ORFN
%ORFN
%ORFN
8QXVHG
%ORFN
%DG%ORFN
8VHU'DWD
%DG%ORFN
8VHU'DWD
8VHU'DWD
8QXVHG
8VHU'DWD
%DG%ORFN