
ADSP-BF59x Blackfin Processor Hardware Reference
16-45
System Reset and Booting
input of the Blackfin processor. It can toggle with each byte transferred or
remain low during the entire procedure. 8-bit data is expected. The 16-bit
mode is not supported.
In SPI slave boot mode, the boot kernel sets the
CPHA
bit and clears the
CPOL
bit in the
SPI1_CTL
register. Therefore the
MOSI
pin is latched on the
falling edge of the
SCK
(SPI clock). For details see
Chapter 13, “SPI-Com-
patible Port Controller”
.
In SPI slave boot mode,
HWAIT
functionality is critical. When high, the
resistor shown in
Figure 16-12
programs
HWAIT
to hold off the host.
HWAIT
holds the host off while the Blackfin processor is in reset. Once
HWAIT
turns inactive, the host can send boot data. The SPI module does not pro-
vide very large receive FIFOs, so the host must test the
HWAIT
signal for
every byte.
Figure 16-14 on page 16-46
illustrates the required program
flow on the host side.
Figure 16-13
shows the initial waveform for an SPI slave boot case. As
soon as the Blackfin processor releases
HWAIT
after reset, the host device
pulls the
SPI1_SS
pin low and starts transmitting data. After the eighth
data word has been received, the boot kernel asserts
HWAIT
again as it has
to process the
DMACODE
field of the first block header. When the host
detects the asserted
HWAIT
it gracefully finishes the transmission of the
on-going word. Then, it pauses transmission until
HWAIT
releases again.
Figure 16-13. Typical SPI Slave Boot Waveforms
HWAIT
SPI1_CLK
SPI1_SS
SPI1_MOSI
SPI1_MISO
RESET
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Summary of Contents for ADSP-BF59x Blackfin
Page 64: ...Development Tools 1 22 ADSP BF59x Blackfin Processor Hardware Reference...
Page 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
Page 244: ...Programming Examples 6 40 ADSP BF59x Blackfin Processor Hardware Reference...
Page 700: ...Programming Examples 16 78 ADSP BF59x Blackfin Processor Hardware Reference...
Page 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...