Device supports 1S-1S-4S mode of OSPI
configuration for fast read operation. This means that command and address are
issued in single bit transfer mode and data access occurs in quad bit mode. The
Command and Address issued are 8 bits and 24 bits followed by 8 dummy cycles. 50MHz is the supported frequency of
operation.
OSPI (4S) Module
Configuration:
- OSPI has two associated
memory regions, the first memory region is dedicated to the configuration
port i.e all internal registers can be programmed and serial transfers made
from the supported external OSPI flash devices. Configuration region is
available at 0x5380_8000 in the SoC address map.
- The second memory region is
associated mainly with the memory-mapped port and is used for communication
directly with external flash devices, the memory region starts at
0x6000_0000. Code will be copied from this region to internal RAM and then
execution starts.
- Serial data clock is derived
from the clock source “SYS_CLK” (200MHz). This clock is divided by a factor
4 and results in a 50MHz interface clock.
- MODE3 of OSPI clock mode is
used, Clock phase and polarity are set to 1, when data is not being
transferred SCK=1, data shifted on falling edge and input on rising
edge.
ROM Sequence:
- Command issued by ROM in this
mode is 0x6B.
- RBL looks for SBL image at
address 0x0000_0000, in case of boot failures due to corrupted image or any
other reason, RBL tries to boot with redundant image as explained in the
section Section 5.5
.
Flash dependency:
- RBL does not perform any
specific action to detect, reset, or power up the OSPI device. OSPI is
assumed to be properly powered and reset completed before every attempt to
boot by RBL.
- RBL also expects the QE bit
is SET in non-volatile configuration so that flash is active in quad mode by
default after POR.