PM0215 datasheet(40/91 Pages) STMICROELECTRONICS

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The STM32 Cortex-M0 instruction set

PM0215

40/91

Doc ID 022979 Rev 1

A carry occurs:

●

If the result of an addition is greater than or equal to 232

●

If the result of a subtraction is positive or zero

●

As the result of a shift or rotate instruction

Overflow occurs if the sign of a result, in bit[31], does not match the sign of the result had

the operation been performed at infinite precision, for example:

●

If adding two negative values results in a positive value

●

If adding two positive values results in a negative value

●

If subtracting a positive value from a negative value generates a positive value

●

If subtracting a negative value from a positive value generates a negative value.

The Compare operations are identical to subtracting, for CMP, or adding, for CMN, except

that the result is discarded. See the instruction descriptions for more information.

Condition code suffixes

The instructions that can be conditional have an optional condition code, shown in syntax

descriptions as B{cond}. An instruction with a condition code is only executed if the

condition code flags in the APSR meet the specified condition. Table 17 shows the condition

codes to use.

You can use conditional execution with the IT instruction to reduce the number of branch

instructions in code.

Table 17 also shows the relationship between condition code suffixes and the N, Z, C, and V

flags.

Table 17.

Condition code suffixes and their relationship with the flags

Suffix

Flags

Meaning

Z = 1

Equal, last flag setting result was zero

Z = 0

Not equal, last flag setting result was non-zero

CS or HS

C = 1

Higher or same, unsigned

≥

CC or LO

C = 0

Lower, unsigned <

N = 1

Negative

N = 0

Positive or zero

V = 1

Overflow

V = 0

No overflow

C = 1 and Z = 0

Higher, unsigned >

C = 0 or Z = 1

Lower or same, unsigned

≤

N = V

Greater than or equal, signed

≥

! = V

Less than, signed <

Z = 0 and N = V

Greater than, signed >

Z = 1 and N

!= V

Less than or equal, signed

≤

Can have any value

Always. This is the default when no suffix is specified.

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