dsp56000 Freescale Semiconductor, Inc, dsp56000 Datasheet - Page 459

• Manufacturer Part Number: dsp56000
• Description: 24-bit Digital Signal Processor Family Manual
• Manufacturer: Freescale Semiconductor, Inc

If the opcode-operand portion of the instruction specifies a given source or destination
register, that same register or portion of that register may be used as a source S1 and/or
S2 in the parallel data bus move operation. This allows data to be moved in the same
instruction in which it is being used as a source operand by a data ALU operation. That
is, duplicate sources are allowed within the same instruction. Note that S1 and S2
may specify the same register.
Class I Example:
Explanation of the Class I Example: Prior to execution, the 56-bit B accumulator con-
tains the value $80:123456:789ABC, the 24-bit X1 register contains the value $000000,
the 16-bit R6 address register contains the value $2020, the 16-bit N6 address offset
register contains the value $0020 and the 24-bit Y memory location Y:$2020 contains the
value $654321. The execution of the parallel move portion of the instruction, B,X1
Y:(R6)–N6,B, moves the 24-bit limited negative saturation constant $800000 into the X1
register since the signed integer portion of the B accumulator was in use, uses the value
in the 16-bit R6 address register to move the 24-bit value in the Y memory location
Y:$2020 into the 56-bit B accumulator with automatic sign extension of the upper portion
of the accumulator (B2) and automatic zeroing of the lower portion of the accumulator
(B0), and finally uses the contents of the 16-bit N6 address offset register to update the
value in the 16-bit R6 address register. The contents of the N6 address offset register
are not affected.
MOTOROLA
R:Y
Y:$2020
ADDL B,A
X1
R6
N6
B
:
:
Before Execution
$80:123456:789ABC
B,X1 Y:(R6)–N6,B
Freescale Semiconductor, Inc.
For More Information On This Product,
Register and Y Memory Data Move
INSTRUCTION DESCRIPTIONS
$000000
$654321
INSTRUCTION SET DETAILS
$2020
$0020
Go to: www.freescale.com
Y:$2020
R6
N6
X1
B
;2 A+B
After Execution
$00:654321:000000
A, update X1,B and R6
$800000
$654321
$2000
$0020
R:Y
A - 193