SH7262/SH7264 Group
Hardware Design Guide
REJ06B0999-0100 Rev. 1.00
Page 14 of 36
Jun. 30, 2010
4.1.4 Boot
Mode
2
Boot mode 2 allows the engineer to boot the SH7264 from NAND flash memory which is connected to the SH7264
NAND flash memory controller. The SH7264 supports the large-block (2048 bytes + 64 bytes) NAND flash memory
with 5-byte address cycles (bigger than 2 Gb density). Number of ECC errors corrected is up to 4. This section
describes the steps to initiate boot mode 2. This section describes the steps in boot mode 2. Steps 1 and 2 are initiated
by the MCU in NAND boot mode, step 3 (optional) is a function of the “loader” that is being executed
(note)
.
NOTE: This step is listed as optional because the “loader” may not actually perform an application load for various
reasons (bad image in FLASH, waiting on Hardware response, waiting on “security” key, etc).
(1) Execute the Internal ROM program to boot
After waking up from power-on reset, CPU executes the program stored in the Internal ROM program to boot
(closed).
(2) Transfer the loader program
CPU transfers an 8-KB loader program from the NAND flash memory connected to the NAND flash memory
controller to the start address of high-speed internal RAM, as the following steps.
It searches the loader program in NAND flash memory, transfers the loader program to the high-speed internal
RAM, and jumps to the entry function of the loader program.
(a) Searches for loader program store blocks (block address 0 to 1023, maximum)
(b) Reads the 8-KB loader program (16 sectors), transfers the loader program to the high-speed internal RAM
(c) Detects errors by ECC
(d) Corrects errors (up to four symbols)
After transferring the loader program is completed, CPU jumps to high-speed internal RAM to start executing the
transferred loader program.
(3) Transfer the application program (optional)
Use the NAND flash memory controller within the loader program to load data from NAND flash memory to
internal RAM or external RAM.
Figure 9 shows the schematic view of boot mode 2.
Internal ROM program to
boot (closed)
Loader program
(8 KB)
High-speed internal RAM
Internal RAM
Application
program
External RAM
NAND flash memory
Application
program
Application
program
NAND
flash memory
controller
H'FFF8 0000
H'FFF8 1FFF
Read request
(2) (a) Search for the
loader program
Read
Read request
SH7264
(1) Execute the program
(2) (b) Loading into high-
speed internal RAM
(3) Loading into external
or internal RAM
Loader program
(8 KB)
(2) (c) Detect error by
ECC
(2) (d) Correct error
(up to four
symbols)
Figure 9 Boot Mode 2 Schematic View