8-Bit Spi Host Boot - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

Booting
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Figure 15-10. 16-Bit SPI Host Packing
The 16-bit SPI host packs or prearranges the data as:
SPI word 1 = 0x5566SPI word 2 = 0x3344
SPI word 3 = 0x1122SPI word 4 = 0xCCDD
SPI word 5 = 0xAABBSPI word 6 = 0x7788
The initial boot of the 256-word loader kernel requires a 16-bit host to
transmit 768 16-bit words. Two packed 16-bit words comprise the 32-bit
word. The SPI DMA count value of 0x180 is equivalent to 384 words.
Therefore, the total number of 16-bit words loaded is 768.

8-bit SPI Host Boot

Figure 15-11 shows 8-bit SPI host packing of 48-bit instructions executed
at PM addresses 0x80000 and 0x80001. For 8-bit hosts, four 8-bit words
pack into the shift register to generate a 32-bit word. The 32-bit word
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32
RXSPI
DMA
MOSI
ADSP-2126x SHARC Processor Hardware Reference
32
INTERNAL
MEMORY
(LOADER KERNEL)
0X80000
0X800FF