dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 60

• Manufacturer Part Number: dsp56800e
• Description: 16-bit Digital Signal Controller Core
• Manufacturer: Freescale Semiconductor, Inc

Data Types and Addressing Modes
Table 3-5 summarizes the various move instructions.
3.3.2.2
Data ALU registers are typically used to hold signed or fractional data because these data types are the
ones that are most often used in DSC algorithms. In contrast, the AGU and program controller registers
almost always manipulate unsigned values because addresses are always positive integer values. When
loading word values into any of these registers, be sure to use the correct type of MOVE instruction to fit
the use of the value.
For loading data ALU registers, the MOVE.W instruction is most frequently used. This instruction loads
the value into the register and sign extends it correctly. Use the MOVEU.W instruction when loading word
values into the AGU and program controller registers. Using this instruction ensures that the word value is
zero extended to the full register width. Table 3-6 shows how MOVE instructions are typically used to load
registers with 16-bit data.
The MOVE.W instruction is always used to store any register to a word location in memory.
3.3.2.3
The rules for accessing peripheral registers are the same as the rules for data memory accesses because
peripheral registers are memory mapped in the data memory space.
3-10
Instruction
MOVEU.W
MOVEU.W
MOVE.W
Suffix
U.BP
U.W
U.B
.BP
.W
.B
.L
Moving Words from Memory to a Register
Accessing Peripheral Registers
MOVE.W X:(R0),A
MOVEU.W X:(R0),R5
MOVE.L X:(R0),A
MOVE.B X:(R0),X0
MOVEU.B X:(R0),X0
MOVE.BP X:(R0),X0
MOVEU.BP X:(R0),X0
Data ALU registers
AGU registers
LA, LC, HWS, OMR, and SR
Table 3-5. Suffixes for DSP56800E Move Instructions
Examples
Table 3-6. Typical 16-Bit-Word Register Loads
Destination
DSP56800E Core Reference Manual
Load register with 1 word from memory, with sign extension
Load register with 1 word from memory, with zero extension
Load register with 1 long from memory, with sign extension; note
that no extension is performed when moving to 24-bit AGU regis-
ters
Load register with 1 byte from memory, with sign extension
Load register with 1 byte from memory, with zero extension
Load register with 1 byte from memory, with sign extension
Load register with 1 byte from memory, with zero extension
Signed words loaded to data ALU registers
Unsigned words loaded to AGU pointer registers
Unsigned words loaded to other control registers
Description
Description
Freescale Semiconductor