Table of Contents
Advertisement
DBcc
Instruction Format:
15
14
13
0
1
0
Instruction Fields:
Condition field — The binary code for one of the conditions listed in the table.
Register field — Specifies the data register used as the counter.
Displacement field — Specifies the number of bytes to branch.
NOTES:
1. Terminating condition is similar to UNTIL loop clauses of high-level languages.
For example, DBMI can be stated decrement and branch until minus.''
2. Most assemblers accept DBRA for DBF when a count terminates the loop (no
condition is tested).
3. A program can enter a loop at the beginning, or by branching to the trailing
DBcc instruction. Entering the loop at the beginning is useful for indexed ad-
dressing modes and dynamically specified bit operations. In this case, the con-
trol index count must be one less than the desired number of loop executions.
However, when entering a loop by branching to the trailing DBcc instruction, the
control count should equal the loop execution count so that the DBcc instruction
will not branch and the main loop will not execute if a zero count occurs.
CPU32
REFERENCE MANUAL
Test Condition, Decrement, and Branch
12
11
10
9
1
CONDITION
DISPLACEMENT
INSTRUCTION SET
8
7
6
5
1
1
0
DBcc
4
3
2
1
0
1
REGISTER
MOTOROLA
0
4-65
Advertisement
Table of Contents
