Podcast
Questions and Answers
What is the purpose of the code provided?
What is the purpose of the code provided?
What is the value of the counter
variable?
What is the value of the counter
variable?
What is the purpose of the STMFD SP!, {R4 - R11}
instruction?
What is the purpose of the STMFD SP!, {R4 - R11}
instruction?
What is the purpose of the LDMIA R0!, {R4 - R11}
instruction?
What is the purpose of the LDMIA R0!, {R4 - R11}
instruction?
Signup and view all the answers
What is the purpose of the STMIA R1!, {R4 - R11}
instruction?
What is the purpose of the STMIA R1!, {R4 - R11}
instruction?
Signup and view all the answers
What is the purpose of the SUBS R3, R3, #1
instruction?
What is the purpose of the SUBS R3, R3, #1
instruction?
Signup and view all the answers
What happens when an 8-bit or 16-bit value is stored from the register to the memory?
What happens when an 8-bit or 16-bit value is stored from the register to the memory?
Signup and view all the answers
Which type of instructions are used to perform read/write operations in memory?
Which type of instructions are used to perform read/write operations in memory?
Signup and view all the answers
When the optional type field is not specified for LDR and STR instructions, how many bits are exchanged between memory and processor registers?
When the optional type field is not specified for LDR and STR instructions, how many bits are exchanged between memory and processor registers?
Signup and view all the answers
In RISC architecture, how are memory access instructions restricted compared to CISC architecture?
In RISC architecture, how are memory access instructions restricted compared to CISC architecture?
Signup and view all the answers
In which addressing mode does the register containing the base address get updated before accessing the memory location?
In which addressing mode does the register containing the base address get updated before accessing the memory location?
Signup and view all the answers
What do Load/Store instructions require for memory addressing?
What do Load/Store instructions require for memory addressing?
Signup and view all the answers
Which type of instructions do Push and Pop belong to?
Which type of instructions do Push and Pop belong to?
Signup and view all the answers
What field can be used to make the execution of LDR and STR instructions conditional?
What field can be used to make the execution of LDR and STR instructions conditional?
Signup and view all the answers
Which addressing mode defines updating the base address before accessing a memory location?
Which addressing mode defines updating the base address before accessing a memory location?
Signup and view all the answers
What is the purpose of the Load instruction in memory access?
What is the purpose of the Load instruction in memory access?
Signup and view all the answers
What addressing modes are defined in the Thumb2 instruction set architecture?
What addressing modes are defined in the Thumb2 instruction set architecture?
Signup and view all the answers
What is the purpose of the PUSH {R7, R8}
instruction?
What is the purpose of the PUSH {R7, R8}
instruction?
Signup and view all the answers
Which direction does the stack grow in?
Which direction does the stack grow in?
Signup and view all the answers
What is the order in which registers are popped from the stack when using the POP instruction?
What is the order in which registers are popped from the stack when using the POP instruction?
Signup and view all the answers
Which of the following is a reason why a stack is needed in a computer system?
Which of the following is a reason why a stack is needed in a computer system?
Signup and view all the answers
What is the relationship between the stack pointer (SP) and the last item pushed onto the stack?
What is the relationship between the stack pointer (SP) and the last item pushed onto the stack?
Signup and view all the answers
How does RISC architecture handle Load/Store Instructions in terms of flags?
How does RISC architecture handle Load/Store Instructions in terms of flags?
Signup and view all the answers
What is the purpose of the POP instruction?
What is the purpose of the POP instruction?
Signup and view all the answers
What is the order in which registers are pushed onto the stack when using the PUSH instruction?
What is the order in which registers are pushed onto the stack when using the PUSH instruction?
Signup and view all the answers
What happens to the stack pointer (SP) register when a data object is pushed onto the stack?
What happens to the stack pointer (SP) register when a data object is pushed onto the stack?
Signup and view all the answers
What happens to the stack pointer (SP) register when a data object is popped from the stack?
What happens to the stack pointer (SP) register when a data object is popped from the stack?
Signup and view all the answers
What is the purpose of the PUSH instruction?
What is the purpose of the PUSH instruction?
Signup and view all the answers
What is the purpose of the POP {R0-R7, R12, R14}
instruction?
What is the purpose of the POP {R0-R7, R12, R14}
instruction?
Signup and view all the answers
What is the purpose of storing the return address in the stack during a subroutine call?
What is the purpose of storing the return address in the stack during a subroutine call?
Signup and view all the answers
Study Notes
Stack Memory Access with PUSH and POP
- The stack is part of main memory, used to store data objects in last-in-first-out (LIFO) buffering format.
- In ARM Cortex-M processor, the stack always operates on 32-bit data.
- The stack pointer contains an address that points to a 32-bit data at the top of the stack.
- As we push data objects onto the stack, the addresses are decremented.
Load and Store Instructions
- Load and Store instructions are used to do a read/write operation in Memory.
- Load is used to take data from a memory location and write that data into a processor register.
- Store is used to store the content of a register into a memory location.
- Load/Store instructions require memory addressing and do not affect the flags.
Immediate Offset Addressing
- Example of immediate offset addressing: LDR R0, [R1] ; Loads R0 from address in R1
- STR R2, [R9, #0x7] ; Stores R2 to a memory location with address R9+7
- Note that R1 and R9 remain unchanged.
Pre-Indexed Offset Addressing Mode
- Syntax: LDR/STR Rt, [Rn, #offset]!
- The register containing the base address is updated before accessing the memory location.
- This updated address is used by the LDR or STR instruction during execution.
- Base address register is updated.
PUSH and POP Instructions
- PUSH instruction copies one or more data objects from a register or a list of registers onto the stack, whose starting address is determined by SP.
- POP instruction copies words from memory and stores them in registers.
- SP decrements (by 4) with each PUSH and increments (by 4) with each POP.
- To push a data object on the stack, the stack pointer is first decremented by 4, and then the 32-bit information is stored at the address specified by SP.
- To pop a data object from the stack, the 32-bit information pointed to by SP is first retrieved, and then the stack pointer is incremented by 4.
Why Do We Need a Stack?
- In subroutine calls, the stack is used to store register values temporarily.
- Registers are saved (pushed to stack) at the start of subroutine, then restored (popped from stack) at the end of the subroutine.
- Each PUSH instruction must have a corresponding POP instruction.
- The stack can be used for parameter passing purposes, if available registers are not enough to pass parameters.
- The stack can be used for declaring local variables.
- The stack can be used for storing the return address.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on key concepts related to memory access instructions in ARM Cortex-M architecture such as load and store instructions, immediate offset addressing, register offset addressing, and more. This quiz is based on Chapter 6 of the book 'ARM Microprocessor Systems: Cortex-M Architecture, Programming, and Interfacing' by Tahir Muhammad and Kashif Javed.