Texas Instruments OMAP5912 Reference Manual page 227

Table 86. Data Swap for 32-Bit Access for MPUI Port
Table 87. Data Swap for 16-Bit Access for MPUI Port
5.1.3 MPUI Strobe and Access Factor
SPRU749A
big endian formats. The swapping logic is controlled by software to have
maximum flexibility to handle different types of data, based on the
BYTE_SWAP_CTL and WORD_SWAP_CTL bits of (MPUI_CONTROL) from
the MPUI.
The ability to turn the endianism on or off makes it more convenient for
peripheral (control) register read/writes. The DSP memory read/write
transactions require conversion of the data, but it is more convenient for the
MPU, OCP-I, and system DMA controller to read and write to registers without
conversion.
The endianism conversion logic only performs byte (8-bit) or 2-byte (16-bit)
swap from big endian to little endian and vice versa without address
manipulation. The swapping mode can be programmed differently according
to information type, information source, and information direction, such as
32-bit or 16-bit data, DSP access, or DSP DMA access and read or write.
Since the MPUI port does not allow accessing with 32-bit data, the MPUI port
logic converts two 16-bit data accesses sequentially when the MPUI accesses
it with 32-bit data. The 2-byte swap is performed during sequential access
conversion.
Table 86 and Table 87 show examples of endian conversion.
32-Bit Accesses
INPUT DATA
OUTPUT DATA
16-Bit Accesses
INPUT DATA
OUTPUT DATA
The MPUI output strobe is an internal signal used to enable bus transactions
between the MPUI and the MPUI port. The strobe active (low) pulse defines
the beginning and end of a transaction. Because the MPUI may be required
to communicate (through the MPUI port) with peripherals of varying speeds,
BYTE_SWAP_CTL
AA BB CC DD
DD CC BB AA
BYTE_SWAP_CTL
00 11
11 00
OMAP3.2 Subsystem
MPU and MPUI Port
WORD_SWAP_CTL
AA BB CC DD
CC DD AA BB
WORD_SWAP_CTL
00 11
00 11
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