Bfchg - T - Motorola DSP56800 Manual

BFCHG
Operation:
(<bit field> of destination) → (<bit field> of destination)BFCHG
(<bit field> of destination) → (<bit field> of destination)BFCHG
Description: Test all selected bits of the destination operand. If all selected bits are set, C is set; otherwise, C is
cleared. Then complement the selected bits and store the result in the destination memory location. The
bits to be tested are selected by a 16-bit immediate value in which every bit set is to be tested and
changed. This instruction performs a read-modify-write operation on the destination memory location
or register and requires two destination accesses.
Usage:
This instruction is very useful in performing I/O and flag bit manipulation.
Example:
BFCHG
Before Execution
X:$FFE2
SR
Explanation of Example:
Prior to execution, the 16-bit X memory location X:$FFE2 contains the value $0010. Execution of the
instruction tests the state of the bits 4, 8, and 9 in X:$FFE2; does not set C (because all of the CCR bits
were not set); and then complements the bits.
Condition Codes Affected:
15 14
LF *
For destination operand SR:
For other destination operands:
Note: If all bits in the mask are set to zero, the destination is unchanged, and the C bit is set.
A-50
Test Bit Field and Change
#$0310,X:<<$FFE2
0010
0001
MR
13 12 11 10 9
* * * * I1
? — Changed if specified in the field
L — Set if data limiting occurred during 36-bit source move
C — Set if all bits specified by the mask are set
Clear if not all bits specified by the mask are set
DSP56800 Family Manual
Assembler Syntax:
#iiii,X:<ea>
#iiii,D
;test and change bits 4, 8, and 9
;in a peripheral register
After Execution
X:$FFE2
SR
CCR
8 7 6 5 4
L
I0 SZ E U
BFCHG
0300
0000
3 2 1 0
C
N Z V