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1 microcontroller 8051 detailed explanation
- 1. Digital IC studied in second Year
- 3. Memory Mapping Circuit 𝐴15 𝐴8 𝐴𝐿𝐸 𝐴𝐷7 𝐴𝐷0 𝑊𝑅 𝑅𝐷 𝐼𝑂/𝑀 𝐸𝑁 𝑳𝑨𝑻𝑪𝑯 𝐴8 − 𝐴15 𝐴0 − 𝐴6 𝐴7 𝐷0− 𝐷7 𝑅 𝐷 𝑊 𝑅 𝐂𝐡𝐢𝐩𝐒𝐞𝐥𝐞𝐜𝐭𝐂𝐢𝐫𝐜𝐮𝐢𝐭 𝐶𝑆 2 𝐶𝑆1 𝐷0− 𝐷7 𝐴0 − 𝐴6 Microprocessor or Microcontroller SRAM 128 X 8 =1024Bit
- 4. Memory mapping 1Kb=1024bits No of lines = 1024/8=128 lines 1Kbit Memory 1Kbits = m X n = 128 X 8 data lines D0 D1 D2 D3 D4 D5 D6 D7 1Kbit Memory W0 W127 }n data lines W0 is first line address and W127 is last line address But do the microprocessor has 128 address lines? NO. 8085 Microprocessor has 16 address lines A0-A15 in which A0 – A6 can be used to select 128 address lines because 27 =128 A0 A1 A2 A3 A4 A5 A6 A7
- 5. What is the use of and ? are chip select signal to select the chip. When =1 and =0, this chip will get selected and the data can be either read from or write into it by sending the proper signal to this SRAM chip. How to generate Chip Select Signal? If Microprocessor has address lines AD0 - AD15. AD0 – AD6 are used to select the address of memory locations of SRAM chip and AD7 – AD15 are used to generate the Chip Select signal.
- 6. What is the use of RD and WR signal? Since it is SRAM, the data can be read from and write into it by using memory read and memory write signal of microprocessor.
- 7. Memory Read and Memory Write signal generator
- 8. Memory Mapping 𝐴15 𝐴8 𝐴𝐿𝐸 𝐴𝐷7 𝐴𝐷0 𝑊𝑅 𝑅𝐷 𝐼𝑂/𝑀 𝐸𝑁 𝑳𝑨𝑻𝑪𝑯 𝐴8 − 𝐴15 𝐴0 − 𝐴6 𝐴7 𝐷0− 𝐷7 𝑅 𝐷 𝑊 𝑅 𝐂𝐡𝐢𝐩𝐒𝐞𝐥𝐞𝐜𝐭𝐂𝐢𝐫𝐜𝐮𝐢𝐭 𝐶𝑆 2 𝐶𝑆1 𝐷0− 𝐷7 𝐴0 − 𝐴6 Microprocessor or Microcontroller SRAM 128 X 8 =1024Bit
- 9. Power on RESET • Highest Priority Interrupt • It should be high for 2 clock cycles • After reset, 8051 starts at 0x0000H RESET
- 10. Program Counter • A register in a computer processor that contains the address (location) of the instruction being executed at the current time. • As each instruction gets fetched, the program counter increases its stored value by 1. • After each instruction is fetched, the program counter points to the next instruction in the sequence. • When the computer restarts or is reset, the program counter normally reverts to 0.
- 11. Stack and Stack Pointer • The stack is a LIFO (last in, first out) data structure implemented in the RAM area. • Used to store addresses and data when the microprocessor branches to a subroutine. • Then the return address used to get pushed on this stack. • Also to swap values of two registers and register pairs we use the stack as well. • Two operations are performed on a stack . • PUSH : The SP register gets decreased by 2 and new data item used to insert on to the top of the stack. POP : the data item will have to be deleted from the top of the stack and the SP register will get increased by the value of 2. The contents of SP specify the top most useful location in the stack.
- 12. Subroutine • When the same function is required more than once in a program, it is frequently written as a subroutine, that is, a subprogram that can be used any number of times by the main program. • Subroutines are a powerful programming construct that allow a program to break down a complex task into smaller, more manageable pieces. • A subroutine is a block of code that can be called from anywhere in the program, and then returns control back to the calling code when it is done.
- 14. Harvard Architecture 1. Separate Storage for Instruction and data. 2. Separate buses are used to fetch instructions and data. 3. the CPU can fetch instruction and read/write data simultaneously. 4. It is basically developed to overcome the bottleneck of Von Neumann’s Architecture. 1. Instructions, and data both are stored in the same memory. 2. Same buses are used to fetch instructions and data. 3. The CPU cannot fetch instruction and data simultaneously. Von Neumann Architecture Main Memory System Central Processing Unit Operational Registers Program Counter Arithmetic and Logic Unit Control Unit Input/Output System Data Instruction Data Address Instruction Address
- 15. RISC : Reduced Instruction Set Architecture 1. Simpler instruction, hence simple instruction decoding. 2. Instruction comes undersize of one word. 3. Instruction takes a single clock cycle to get executed. 4. More general-purpose registers. 5. Simple Addressing Modes. 6. Fewer Data types. CISC : Complex Instruction Set Architecture 1. Complex instruction, hence complex instruction decoding. 2. Instructions are larger than one-word size. 3. Instruction may take more than a single clock cycle to get executed. 4. Less number of general- purpose registers as operations get performed in memory itself. 5. Complex Addressing Modes. 6. More Data types.
- 16. RISC : Reduced Instruction Set Architecture Advantages • Simpler instructions: RISC processors use a smaller set of simple instructions, which makes them easier to decode and execute quickly. This results in faster processing times. • Faster execution: Because RISC processors have a simpler instruction set, they can execute instructions faster than CISC processors. • Lower power consumption: RISC processors consume less power than CISC processors, making them ideal for portable devices. CISC : Complex Instruction Set Architecture Advantages • Reduced code size: CISC processors use complex instructions that can perform multiple operations, reducing the amount of code needed to perform a task. • More memory efficient: Because CISC instructions are more complex, they require fewer instructions to perform complex tasks, which can result in more memory-efficient code. • Widely used: CISC processors have been in use for a longer time than RISC processors, so they have a larger user base and more available software.
- 17. RISC : Reduced Instruction Set Architecture Disadvantages • More instructions required: RISC processors require more instructions to perform complex tasks than CISC processors. • Increased memory usage: RISC processors require more memory to store the additional instructions needed to perform complex tasks. • Higher cost: Developing and manufacturing RISC processors can be more expensive than CISC processors. CISC : Complex Instruction Set Architecture Disadvantages • Slower execution: CISC processors take longer to execute instructions because they have more complex instructions and need more time to decode them. • More complex design: CISC processors have more complex instruction sets, which makes them more difficult to design and manufacture. • Higher power consumption: CISC processors consume more power than RISC processors because of their more complex instruction sets.
- 18. Primary Memory • The primary memory of a computer is the main memory that is utilized to store data temporarily. • Primary memory is temporary. • Primary memory is faster than secondary memory because it is directly accessible to the CPU. • Primary memory is directly accessible by Processor/CPU. • Nature of Parts of Primary memory varies, RAM- volatile in nature. ROM- Non-volatile. Secondary memory • Secondary memory defines to additional storage devices that are utilized to store data permanently. • Secondary memory is permanent. • Secondary memory is non- volatile, which means it retains data even when the power is off. • Secondary memory is not directly accessible by the CPU. • It’s always Non-volatile in nature.
- 19. Primary Memory • Primary memory devices are more expensive than secondary storage devices • The memory devices used for primary memory are semiconductor memories. • It can hold data/information currently being used by the processing unit. • The capacity of primary memory is usually within the range of 16 to 32 GB. Secondary memory • Secondary memory devices are less expensive when compared to primary memory devices. • The secondary memory devices are magnetic and optical memories. • It can hold data/information that are not currently being used by the processing unit. • It stores a considerable amount of data and information. The capacity of secondary memory ranges from 200 GB to some terabytes
- 20. Primary Memory • Primary memory is also known as Main memory or Internal memory. • It can be accessed by a data bus. • Examples: RAM, ROM, Cache memory, PROM, EPROM, Registers, etc. Secondary memory • Secondary memory is also known as External memory or Auxiliary memory. • It can be accessed using I/O channels. • Examples: Hard Disk, Floppy Disk, Magnetic Tapes , etc
- 21. Cache Memory • The most important use of cache memory is that it is used to reduce the average time to access data from the main memory. • The concept of cache works because there exists locality of reference (the same items or nearby items are more likely to be accessed next) in processes.
- 22. Characteristics of Cache Memory • Extremely fast memory type that acts as a buffer between RAM and the CPU. • Holds frequently requested data and instructions, ensuring that they are immediately available to the CPU when needed. • Costlier than main memory or disk memory but more economical than CPU registers. • Used to speed up processing and synchronize with the high-speed CPU.
- 23. Cache Performance • If the processor finds that the memory location is in the cache, a Cache Hit has occurred and data is read from the cache. • If the processor does not find the memory location in the cache, a cache miss has occurred. For a cache miss, the cache allocates a new entry and copies in data from the main memory, then the request is fulfilled from the contents of the cache.
- 24. Virtual memory with Memory Management • Virtual memory is a memory management technique used by operating systems to give the appearance of a large, continuous block of memory to applications, even if the physical memory (RAM) is limited. It allows larger applications to run on systems with less RAM.
- 25. Virtual memory with Memory Management • The main objective of virtual memory is to support multiprogramming, The main advantage that virtual memory provides is, a running process does not need to be entirely in memory. • Programs can be larger than the available physical memory. Virtual Memory provides an abstraction of main memory, eliminating concerns about storage limitations. • A memory hierarchy, consisting of a computer system’s memory and a disk, enables a process to operate with only some portions of its address space in RAM to allow more processes to be in memory.
- 26. Types of virtual memory • Paging – Paging divides memory into small fixed-size blocks called pages. When the computer runs out of RAM, pages that aren’t currently in use are moved to the hard drive, into an area called a swap file. The swap file acts as an extension of RAM. When a page is needed again, it is swapped back into RAM, a process known as page swapping. This ensures that the operating system (OS) and applications have enough memory to • Segmentation – Segmentation divides virtual memory into segments of different sizes. Segments that aren’t currently needed can be moved to the hard drive. The system uses a segment table to keep track of each segment’s status, including whether it’s in memory, if it’s been modified, and its physical address. Segments are mapped into a process’s address space only when needed.run.
- 27. Feature Virtual Memory Physical Memory (RAM) Definition An abstraction that extends the available memory by using disk storage The actual hardware (RAM) that stores data and instructions currently being used by the CPU Location On the hard drive or SSD On the computer’s motherboard Speed Slower (due to disk I/O operations) Faster (accessed directly by the CPU) Capacity Larger, limited by disk space Smaller, limited by the amount of RAM installed Cost Lower (cost of additional disk storage) Higher (cost of RAM modules) Data Access Indirect (via paging and swapping) Direct (CPU can access data directly) Volatility Non-volatile (data persists on disk) Volatile (data is lost when power is off)