www.digiembedded.com
119
Memory Controller
Chip select 1 memory configuration
You can configure the memory width and chip select polarity of static memory chip
select 1 by using selected input signals. This allows you to boot from chip select 1.
These are the bootstrap signals:
boot_strap[4:3]: Memory width select
gpio[49]: Chip select polarity
boot_strap[0]: Byte lane enable_n/write_enable_n for byte-wide devices
Example: Boot from flash, SRAM mapped after boot
The system is set up as:
Chip select 1 is connected to the boot flash device.
Chip select 0 is connected to the SRAM to be remapped to 0x00000000 after
boot.
The boot sequence is as follows:
1At power-on, the reset chip select 1 is mirrored into chip select 0 (and chip
select 4). The following signals are configured so the nonvolatile memory device
can be accessed:
boot_strap[4:3]
gpio[49]
2When the power-on reset (reset_n) and AHB reset (HRESETn) go inactive, the
processor starts booting from 0x00000000 in memory.
3The software programs the optimum delay values in the flash memory so the
boot code can run at full speed.
4The code branches to chip select 1 so the code can continue executing from the
non-remapped memory location.
5The appropriate values are programmed into the memory controller to configure
chip select 0.
6The address mirroring is disabled by clearing the address mirror (M) field in the
Control register (see page 205).
7The ARM reset and interrupt vectors are copied from flash memory to SRAM that
can then be accessed at address 0x00000000.