Little-Endian Versus Big-Endian Data Format; Dsp Subsystem Endianess - Texas Instruments OMAP5910 Reference Manual

Table 84. HOM_R and HOM_P Bits in DSP Core Register ST3_55
Bits Field
9 HOM_R
8 HOM_P
10

DSP Subsystem Endianess

10.1 Endianess Within OMAP
Table 85. Little-Endian versus Big-Endian Data Format
32-bit Value:
0x1234 5678
Little
4 LSBs of
Endian
Byte Address
XX00b 0x78
XX01b 0x56
XX10b 0x34
XX11b 0x12
Note: X = Don't care.
SPRU890A
Value Description
Memory access mode bit. This bit determines whether the MPUI port
operates in SAM_M or HOM_M.
0 SAM_M. The DSP SARAM and DARAM are shared by the MPUI and
the DSP controllers.
1 HOM_M. The DSP SARAM can be configured for exclusive access by
the MPUI. The API_SIZE bits of the MPUI_DSP_CONFIG register
specify the amount of SARAM that is dedicated to MPUI accesses.
DSP public peripherals access mode bit. This bit determines whether
the MPUI port operates in SAM_P or HOM_P.
0 SAM_P. DSP public peripherals are shared by the MPU and DSP
domains.
1 HOM_P. DSP public peripherals are owned only by the MPU domain.
The DSP subsystem modules operate in Big-Endian mode, contrary to the rest
of the OMAP modules (including the MPU core and system DMA), which
operate in Little-Endian mode. Shared data between the DSP subsystem and
the rest of the OMAP modules must be converted to their respective formats
before any processing. This process is called endianess conversion.
Table 85 details the Little- and Big-Endian data formats, assuming a
byte-addressable architecture.
Big
Endian
0x12
0x34
0x56
0x78
MPU Interface Port / DSP Subsystem Endianess
16-bit Value:
0x1234
Little Big
Endian Endian
0x34 0x12
0x12 0x34
DSP Subsystem Endianess
8-bit Value:
0x12
Little Big
Endian Endian
0x12 0x12
DSP Subsystem 197