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Specific Blackfin Boot Modes
8-Bit Flash/PROM Boot (BMODE = 001)
Booting from 8-bit flash requires the same
flash. The two modes are differentiated by the first byte read in. While
booting from 8-bit flash/PROM sounds cheaper and may result in smaller
board space, there are also some disadvantages compared to the 16-bit
mode: 8-bit mode supports only up to 512k byte devices directly, whereas
16-bit mode supports up to 1M byte. Because code execution from 8-bit
external memory is not supported, in 8-bit mode the usage of the
flash/PROM device is most likely restricted to booting purposes. The boot
kernel assumes these conditions for the flash boot mode (
• Asynchronous Memory Bank (AMB) 0 enabled
• 16-bit packing for AMB 0 enabled
• Bank 0
• Bank 0 hold time (read/write deasserted to
3 cycles
• Bank 0 read/write access times = 15 cycles
Since the EBIU on the Blackfin processor is 16 bits wide (hence no
), an 8-bit flash/PROM occupies only the lower 8 bits of the data
ADDR[0]
bus (
).
Figure 19-11
D[7:0]
the Blackfin processor and an 8-bit flash/PROM.
19-36
is set to active high
RDY
illustrates the pin-to-pin connections between
ADSP-BF537 Blackfin Processor Hardware Reference
settings as with 16-bit
BMODE
BMODE
deasserted) =
AOE
=
):
001
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