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Integer Instructions
MOTOROLA M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL 4-85
cpDBcc Test Coprocessor Condition cpDBcc
Decrement and Branch
(MC68020, MC68030)
Operation: If cpcc False
Then (Dn – 1 Dn; If Dn – 1 Then Scan PC + d
n
PC)
Assembler
Syntax: cpDBcc Dn, < label >
Attributes: Size = (Word)
Description: If the specified coprocessor condition is true, execution continues with the
next instruction. Otherwise, the low-order word in the specified data register is
decremented by one. If the result is equal to – 1, execution continues with the next
instruction. If the result is not equal to – 1, execution continues at the location indicated
by the value of the scan PC plus the sign-extended 16-bit displacement. The value of
the scan PC is the address of the displacement word. The displacement is a twos
complement integer that represents the relative distance in bytes from the scan PC to
the destination program counter. The coprocessor determines the specific condition
from the condition word that follows the operation word.
Condition Codes:
Not affected.
Instruction Format:
Instruction Fields:
Coprocessor ID field—Identifies the coprocessor for this operation; coprocessor ID of
000 results in an F-line exception for the MC68030.
Register field—Specifies the data register used as the counter.
Coprocessor Condition field—Specifies the coprocessor condition to be tested. This
field is passed to the coprocessor, which provides directives to the main
processor for processing this instruction.
Displacement field—Specifies the distance of the branch (in bytes).
1514131211109876543210
1111
COPROCESSOR
ID
001001 REGISTER
0000000000 COPROCESSOR CONDITION
OPTIONAL COPROCESSOR-DEFINED EXTENSION WORDS
16-BIT DISPLACEMENT
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