Big-Endian Access Of Little-Endian Data; Endianess Conversion Modules - Texas Instruments OMAP5910 Reference Manual

Table 86. Big-Endian Access of Little-Endian Data
4 LSBs of
Byte Address
XX00b
XX01b
XX10b
XX11b
Note: X = Don't care.
10.3

Endianess Conversion Modules

SPRU890A
32-bit Value
(0x1234 5678)
stored as Little Single 32-Bit Read
Endian
0x78 0x1234 5678
0x56
0x34
0x12
There are three distinct scenarios where the DSP subsystem modules and the
rest of the OMAP modules access the same resources, and endianess
conversion might be required.
MPU core or system DMA accesses to the DSP subsystem internal
-
memory via the MPU Interface (MPUI). Endianess conversion is
performed in the MPUI.
DSP core or DSP DMA accesses to DSP external memory via the DSP
-
memory management unit (MMU) and the traffic controller. Endianess
conversion is performed in the DSP MMU.
DSP core and MPU core accesses to shared peripherals. No endianess
-
conversion is performed, as both the DSP core and the MPU core see the
same data.
Because the endianess conversion is performed in hardware, data swapping
is transparent to software. This reduces the software overhead needed to
format the data. The swapping logic can be disabled and the conversion
handled by software, as desired.
Two 16-Bit Read
Access Accesses
0x5678
0x1234
DSP Subsystem Endianess
Four 8-Bit Read
Accesses
0x78
0x56
0x34
0x12
DSP Subsystem 199