Understanding Multiplexing and Memory in Microcontrollers

20SE02CE032 Lathiya Nemish EMBEDDED SYSTEM SEIT3022 Assignment – 01 1) What is a difference between microprocessor and microcontroller? Ans: 1) Microprocessor consists of only a Central Processing Unit, whereas Micro 2) 3) 4) 5) Controller contains a CPU, Memory, I/O all integrated into one chip. Microprocessor is used in Personal Computers whereas Micro Controller is used in an embedded system. Microprocessor uses an external bus to interface to RAM, ROM, and other peripherals, on the other hand, Microcontroller uses an internal controlling bus. Microprocessors are based on Von Neumann model Micro controllers are based on Harvard architecture Microprocessor is complicated and expensive, with a large number of instructions to process but Microcontroller is inexpensive and straightforward with fewer instructions to process. 2)Why cache memory and register memory cannot be considered as primary memory? Define with example. Ans:  Primary Memory is the memory system that allows storing instruction and data on which the system is working in the present time.  Cache memory is the one type of memory system that has a high speed of superconductor. It helps in enhancing the CPU speed to a top notch. The cache memory stores the data and instruction that are used frequently by a user. It prevents regular transformation with the main memory and the user can fetch data from it at a higher rate. A small part of program or data is stored up in it that allows CPU to access it easily.  Registers are the high-speed accessible storage elements. The processor accesses the registers within one CPU clock cycle. So we can say that processor can access registers faster than the main memory. The basic difference between the register and memory is that the register holds the data that CPU is currently processing whereas, the memory holds program instruction and data that the program requires for execution. 3) Write in detail about feature of 8051 microcontroller with reference to the context where it is used. Ans: The main features of the 8051-microcontroller architecture include the following:  8-bit CPU through two Registers A & B.  8K Bytes – Internal ROM and it is a flash memory that supports while programming the system.  256 Bytes – Internal RAM where the first RAM with 128 Bytes from 00H to 7FH is once more separated into four banks through 8 registers in every bank, addressable registers -16 bit & general-purpose registers – 80.  The remaining 128 bytes of the RAM from 80H to FFH include Special Function Registers (SFRs). These registers control various peripherals such as Serial Port, Timers, all I/O Ports, etc.  Interrupts like External-2 & Internal-3  Oscillator & CLK Circuit.  Control Registers like PCON, SCON, TMOD, TCON, IE, and IP.  16-bit Timers or Counters -2 like T0 & T1.  Program Counter – 16 bit & DPRT (Data Pointer).  I/O Pins – 32 which are arranged like four ports such as P0, P1, P2 & P3.  Stack Pointer (SP) – 8bit & PSW (Processor Status Word).  Serial Data Tx & Rx for Full-Duplex Operation. 4)Why the name of 8051 start with digit 8 and 0? Ans: 8 represents b-bit processor and 0 represents belongs to low power Micro-controller family 8000. 5)What is the role of character set in processor? Justify your answer for 8- bit process and also explain the input process. Ans:  A character set defines the valid characters that can be used in source programs or interpreted when a program is running.  8-bit is an early computer hardware device or software program that is capable of transferring eight bits of data at the same time.  It consists of are four parallel 8-bit ports, which are programmable as well as addressable as per the requirement. 6) What do you mean by multiplexing? How is it different from demultiplexing? Explain multiplexing and demultiplexing with references to the microcontroller. Ans:  Multiplexing is the process of combining multiple signals into one signal, over a shared medium. If analog signals are multiplexed, it is Analog Multiplexing and if digital signals are multiplexed, that process is Digital Multiplexing.  Multiplexer refers to a type of combinational circuit that accepts multiple inputs of data but provides only a single output. The demultiplexer refers to the type of combinational circuit that accepts just a single input but directs it through multiple outputs. A Multiplexer performs conversion from parallel to serial.  The System-On-Chip (Microcontroller) has a lot of functionality but a limited number of pins (or pads). Even though a single pin can only perform one function at a time, they can be configured internally to perform different functions. This is called pin multiplexing. i.e one pin can perform multiple functions. The regular function of a pin is to perform parallel I/O. Most of the pins have an alternative function. 7) What is Latch and how is it different from flip flop? Ans:  Latch is an electronic logic circuit with two stable states i.e., it is a bistable multivibrator. Latch has a feedback path to retain the information. Hence a latch can be a memory device. Latch can store one bit of information as long as the device is powered on. When enable is asserted, latch immediately changes the stored information when the input is changed i.e., they are level triggered devices. It continuously samples the inputs when the enable signal is on.  The major difference between flip-flop and latch is that the flipflop is an edge-triggered type of memory circuit while the latch is a level- triggered type. It means that the output of a latch changes wheneverthe input changes. On the other hand, the latch only changes its state whenever the control signal goes from low to high and high to low. 8) What is difference between lower order bus and higher orer bus? Ans:  Low order means the low end, and high order means the high end. Think of a decimal constant - lets pick 1234 - 12 would be considered the high order and 34 would be considered the low order.  In the 8085, the address bus is A15 (high order bit) to A0 (low order bit). Since the processor is byte organized, you can say this as A15-A8 is the high order byte and A7-A0 is the low order byte. 9) Explain XTAL1 and XTAL2. Ans:  The 8051 has an on-chip oscillator but requires an external crystal to run it  A quartz crystal oscillator is connected to inputs XTAL1 (pin19) and XTAL2(pin18)  The quartz crystal oscillator also needs two capacitors of 30 pF value  The original 8051 operates at 12 MHZ.  If you use a frequency source other than a crystal oscillator, such as a TTL oscillator:  It will be connected to XTAL1  XTAL2 is left unconnected