dsp56800 Freescale Semiconductor, Inc, dsp56800 Datasheet - Page 318

• Manufacturer Part Number: dsp56800
• Description: 16-bit Digital Signal Controllers
• Manufacturer: Freescale Semiconductor, Inc

LEA
Operation:
ea → D
Description: The address calculation specified is executed and the resulting effective address (ea) is stored in the
Example:
Explanation of Example:
Condition Codes Affected:
Instruction Fields:
Timing:
Memory:
A-88
Operation
LEA
destination register (D). The source address register and the update mode used to compute the updated
address are specified by the effective address. The source address register specified in the effective ad-
dress is not updated. All update addressing modes may be used. The new register contents are available
for use by the immediately following instruction.
LEA
Prior to execution, the 16-bit address register R0 contains the value $8001, the 16-bit address register
N contains the value $0C01, and the 16-bit modulo register M01 contains the value $1000. Execution
of the LEA (R0)+N instruction adds the contents of the R0 register to the contents of the N register
and stores the resulting updated address in the R0 address register. The addition is performed using
modulo arithmetic since it is done with the R0 register and M01 is not equal to $FFFF. No wraparound
occurs during the addition because the result falls within the boundaries of the modulo buffer.
The condition codes are not affected by this instruction.
2+ea oscillator clock cycles
1+ea program words
Before Execution
M01
R0
N
(Rn+xxxx)
Operands
(R2+xx)
(Rn)+N
(SP-xx)
(Rn)+
(Rn)-
(R0)+N
0C01
8001
1000
Load Effective Address
DSP56800 Family Manual
C
2
2
2
2
2
4
Assembler Syntax:
LEA
; update R0 using (R0)+N
W
1
1
1
1
1
2
Increment the Rn pointer register
Decrement the Rn pointer register
Add register N to Rn and store the result in Rn.
Add a 6-bit unsigned immediate value to R2 and store in
the R2 Pointer
Subtract a 6-bit unsigned immediate value from SP and
store in the SP register
Add a 16-bit signed immediate value to the specified
source register.
After Execution
ea
M01
R0
N
Comments
8C02
0C01
1000
Freescale Semiconductor
LEA