SH7262/SH7264 Group
Hardware Design Guide
REJ06B0999-0100 Rev. 1.00
Page 12 of 36
Jun. 30, 2010
4. Operating
Mode
Control
The SH7264 has four boot modes and four clock operating modes. These modes can be set by pins MD_BOOT1,
MD_BOOT0, MD_CLK1, and MD_CLK0.
4.1 Boot
Modes
4.1.1
Setting the External Pins to Specify Boot Mode
When the RES# pin is driven low, the SH7264 specifies boot mode by external pins. Table 4 lists the relationship
between external pins and boot modes.
Table 4 Relationship between External Pins and Boot Modes
MD_BOOT1 MD_BOOT0 Boot
Mode
0
0
Boots the MCU from the memory connected to CS0 space (Boot mode 0)
0 1
Boots the MCU from serial flash memory connected to the Renesas Serial
Peripheral Interface channel 0 at high speed (Boot mode 1)
1 0
Boots the MCU from NAND flash memory connected to the NAND flash
memory controller (Boot mode 2)
1 1
Boots the MCU from serial flash memory connected to the Renesas Serial
Peripheral Interface channel 0 at low speed (Boot mode 3)
4.1.2 Boot
Mode
0
Boot mode 0 allows the engineer to boot the SH7264 from memory which is connected to CS0 space. This section
describes the steps initiated by the MCU in boot mode 0
(note)
.
(1) Retrieve the execution start address from the exception handling vector table
After waking up from power-on reset, CPU retrieves the initial values of the program counter (PC) and stack pointer
(SP) from the exception handling vector table which is allocated to the CS0 space-connected memory.
(2) Start executing the program
CPU starts executing the program from the PC address retrieved.
NOTE: There is often misunderstanding between booting and execution. Boot Mode 0 actually allows the execution
“in place” (i.e. directly from NOR FLASH). The engineer is not required to move code into RAM when in Boot mode 0,
nor does it preclude the user from copying and executing the code from RAM (the common notion of booting). NAND
and SPI mode are true “boot modes” where the code must be moved from the non-volatile (FLASH) to RAM (internal
or external) to be executed.