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Questions and Answers
What is the purpose of the Status Register (SREG) in the context of Mega AVR devices?
Which register can be used as an address pointer to read from and/or write to flash program memory in Mega AVR devices?
What is the primary function of the Stack Pointer (SP) in Mega AVR devices?
How is the Stack organized in terms of memory locations?
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Which flag must be set to 1 in the Status Register (SREG) to enable interrupts in Mega AVR devices?
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Which registers can form 16-bit address pointers for addressing data memory in Mega AVR devices?
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What information does the Status Register (SREG) contain?
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Study Notes
Atmel ATmega328P Microcontroller
- 8-bit Atmel ATmega328/P microcontroller used in ARDUINO UNO R3 Board
- Introduced in 1996, adopts a modified Harvard architecture
- Program and data stored in separate physical memory address spaces, but can read data from program memory using special instructions
AVR CPU
- AVR family of microcontrollers divided into four subgroups: Tiny AVR, Mega AVR, XMega AVR, and Application-specific AVR
- AVR CPU based on Reduced Instruction Set Computing (RISC) architecture
- Single cycle execution, 32 general purpose registers
ATmega328P Features
- Low-power CMOS 8-bit microcontroller
- 28/32 pins
- CMOS: Complementary Metal-Oxide-Semiconductor
- RISC (Reduced Instruction Set Computing) architecture
Endianness
- Little-endian: least significant byte of data is placed at byte with lowest address
- Big-endian: most significant byte of data is placed at byte with lowest address
Packages
- Different ATMega328 packages: Micro Leadframe or Quad-flat no-leads (MLF/VQFN), Quad-flat Package (TQFP), Dual in-line Package (DIP)
Pin Descriptions
- Pin descriptions available on Atmel ATmega328/P pages 17-20
AVR CPU Core
- ALU (Arithmetic Logic Unit) performs arithmetic operations between registers or between a register and an immediate
- 32 general purpose registers (R0-R31) directly connected to ALU
- 8-bit Status Register (SREG) stores information about the result of the most recently executed arithmetic instruction
- Program Counter (PC) and Instruction Register
- Instruction Decoder and Stack Pointer (SP)
ALU Operations
- Divided into three main categories: Arithmetic, Logical, and Bit-functions
- Some implementations of ALU provide a powerful multiplier supporting both signed/unsigned multiplication and fractional format
AVR CPU Registers
- 32 general-purpose registers with single clock cycle access time
- Six of the 32 registers can form 16-bit address pointers (X, Y, and Z pointers) for addressing data memory
- Z register can also be used as an address pointer to read from and/or write to the flash program memory, signature rows, fuses, and lock bits
Status Register (SREG)
- Contains information about the result of the most recently executed arithmetic instruction
- Bit 7 (I): Global Interrupt Enable, must be set to 1 to enable interrupts, cleared to 0 to disable interrupts
AVR Stack Pointer (SP)
- Address of the Stack area where the interrupts and subroutine Stacks are located
- SP points to the data SRAM Stack area
- The Stack grows from higher to lower memory locations
- SP is implemented as two 8-bit registers
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Description
Test your knowledge about the Atmel ATmega328P microcontroller, including its CPU, instructions, memory model, addressing modes, and relation to Arduino UNO R3 board. This quiz aligns with CLO 2 of the Introduction to Embedded Systems course by Dr.Abdulmalik Alwarafy for Spring 2024.
