Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet

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SAM4E [DATASHEET]

Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14

 

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For B, BL, CBNZ, and CBZ instructions, the value of the PC is the address of the current instruction plus 4 
bytes. 

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For all other instructions that use labels, the value of the PC is the address of the current instruction plus 4 
bytes, with bit[1] of the result cleared to 0 to make it word-aligned.

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Your assembler might permit other syntaxes for PC-relative expressions, such as a label plus or minus a 
number, or an expression of the form [PC, #number]. 

Most data processing instructions can optionally update the condition flags in the Application Program Status
Register (APSR) according to the result of the operation, see 

instructions update all flags, and some only update a subset. If a flag is not updated, the original value is
preserved. See the instruction descriptions for the flags they affect.

An instruction can be executed conditionally, based on the condition flags set in another instruction, either:

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Immediately after the instruction that updated the flags

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After any number of intervening instructions that have not updated the flags.

Conditional execution is available by using conditional branches or by adding condition code suffixes to
instructions. See 

 for a list of the suffixes to add to instructions to make them conditional instructions.

The condition code suffix enables the processor to test a condition based on the flags. If the condition test of a
conditional instruction fails, the instruction:

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Does not execute

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Does not write any value to its destination register

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Does not affect any of the flags

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Does not generate any exception.

Conditional instructions, except for conditional branches, must be inside an If-Then instruction block. See 

more information and restrictions when using the IT instruction. Depending on the vendor, the assembler might
automatically insert an IT instruction if there are conditional instructions outside the IT block.

The CBZ and CBNZ instructions are used to compare the value of a register against zero and branch on the result.

This section describes:

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.

The APSR contains the following condition flags:

N 

Set to 1 when the result of the operation was negative, cleared to 0 otherwise.

Z 

Set to 1 when the result of the operation was zero, cleared to 0 otherwise.

C 

Set to 1 when the operation resulted in a carry, cleared to 0 otherwise.

V 

Set to 1 when the operation caused overflow, cleared to 0 otherwise.

For more information about the APSR, see 

.

A carry occurs:

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If the result of an addition is greater than or equal to 2

32

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If the result of a subtraction is positive or zero

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As the result of an inline barrel shifter operation in a move or logical instruction.

An overflow occurs when the sign of the result, in bit[31], does not match the sign of the result, had the operation
been performed at infinite precision, for example:

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If adding two negative values results in a positive value