MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
897
Preliminary—Subject to Change Without Notice
23.4.9.2.7
Conditional ALU/MDU Operation Execution
The 3-bit field AS/CE allows conditional execution of arithmetic operation, as shown in
same field can also be used for overriding the size of A-Source (see
Section 23.4.9.2.8, “A-Source Size
Other operations not related to ALU/MDU in the same microinstruction are not affected by the AS/CE
field.
If a conditional operation is selected, there is no A-Source size override; similarly, when size override for
A-Source is selected, the ALU/MDU operation executes unconditionally.
When a conditional ALU/MDU operation is not executed:
•
the destination register is not updated. If the destination is CHAN, no actions associated with
CHAN assignment occur (see
Section , “Channel Selection Register - CHAN
).
•
the ALU and MDU flags are not updated.
•
MDU does not start any operation, i.e., MACH and MACL are not updated.
•
SR does not shift.
•
T4ABS-selected read-match does not occur.
23.4.9.2.8
A-Source Size Override
Some values if the AS/CE field are used for A-Source Size Override, as shown in
Table 23-71. ALU/MDU Conditional Execution
AS/CE
Meaning
000
used for A-Source size override (see
Section 23.4.9.2.8, “A-Source Size Override
)
001
010
execute if C = 1
011
execute if C = 0
100
execute if Z = 1
101
execute if Z = 0
110
execute if N = 1
111
execute unconditionally/no size override
Table 23-72. A-Source Size Override
AS/CE
Meaning
000
A-source size override to 8 bits
001
A-source size override to 16 bits
010
used for conditional execution (see
Section 23.4.9.2.7, “Conditional ALU/MDU Operation
011
100
101
110
111
execute unconditionally/no size override