tags:
- notes
- lecture
- bsu
- spring-2025
- ece-330
- microprocessors
- school
source: https://boisestatecanvas.instructure.com/courses/36351/files/folder/Lectures?preview=17499338
created: 2025-02-05What is a subroutine?
A subroutine is a block of code that performs a task based on some arguments and optionally returns a result.
What is the Branch and Link (BL) instruction do?
The BL instruction calls subroutines by using the Link Register (LR) to hold the return-from address.
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CBZ R3, label - Compare R3 to zero. If R3 == 0 (Z = 1), then branch to label. Otherwise, do the following instruction.CBNZ R3, label - Compare R3 to zero. If R3 != 0 (Z = 0), then branch to label. Otherwise, do the following instruction.CMP R3, R4 - Compare R3 to R4 using R3 - R4 and update the status flags. If R3 < R4, then set the N flag to 1. If R3 == R4, then set the Z flag to 1.CMP R3, #15 - Compare R3 to 15 using R3 - 15 and update the status flags...CMN R3, R4 - Compare negative R3 to R4 using R3+R4 and update the status flags. If R3 < -R4, then set the N flag to 1. If R3 == -R4, then set the Z to 1.What are the different branch instructions and their behavior?
The different branch instructions and their behavior include:
B, label - Go to the code starting at label.BEQ label - Go to the code starting at label if Z == 1 (equal). BNE label - Go to the code starting at label if Z == 0 (not equal).BLT label - Go to the code starting at label if N == 1 (less than).BGT label - Go to the code starting at label if N == 0 (greater than).BGE label - Go to the code starting at label if N == 0 or Z == 1 (greater than or equal to).