Direct Code Execution - Analog Devices ADSP-BF506F Hardware Reference Manual

Basic Booting Process
Table 24-5. Header for a Single Block Boot Stream (Cont'd)
Field
BYTE COUNT
ARGUMENT
With the
BFLAG_FIRST
next-DXE pointer. This is a relative pointer to the next free source address
or to the next DXE start address in a multi-DXE stream.

Direct Code Execution

Applications may want to avoid long booting times and start code execu-
tion directly from 16-bit flash. This feature is called direct code execution.
This is a special case of boot termination that replaces the no-boot/bypass
mode in the ADSP-BF53x Blackfin processors.
An initial boot block header is needed for the processor to fetch and exe-
cute program code from the boot device as early as possible. The safety
mechanisms of the block, such as the header signature and the XOR
checksum, avoid unpredictable processor behavior due to the boot mem-
ory not being programmed with valid data yet. The boot kernel first loads
the first block header and checks it for consistency. If the block header is
corrupted, the boot kernel goes into a safe idle state and does not start
code execution.
If the initial block header checks good, the boot kernel interrogates the
block flags. If the block has the
immediately terminates and jumps directly to the address stored in the
register. To cause the boot kernel to customize the
EVT1
advance, the initial blocks must also have the
TARGET ADDRESS
TARGET ADDRESS
application.
24-22
Value Comments
0x0000 0100 256 bytes of code
0x0000 0100 Functions as next-DXE pointer in multi-DXE boot streams
flag set, the
BFLAG_FINAL
field is then copied to the
field of the initial block defines the start address of the
ADSP-BF50x Blackfin Processor Hardware Reference
field functions as the
ARGUMENT
flag set, the boot kernel
BFLAG_FIRST
register. In this way, the
EVT1
register in
EVT1
flag set. The