QUESTION 6: MICROCONTROLLERS 6.1 State TWO uses of a microcontroller as used in commercial devices - NSC Electrical Technology Digital - Question 6 - 2024 - Paper 1

The block diagram in FIGURE 6.2 represents a Microcontroller.

The Control Bus is used primarily for the CPU to issue control instructions to both memory and input/output ports.

The Data Bus acts as the 'highway' through which all data is transferred, sent, and received between the CPU, memory, and input/output ports.

An interface is a shared boundary across which two separate components of a computer system exchange information.

When data enters the Current Instruction Register (CIR) from the Memory Data Register (MDR), it is divided into two parts. The first part contains the opcode (instruction type), and the second part holds the address of the data that will be used with that instruction, making it ready for execution.

The Accumulator is used to store arithmetic operation results temporarily. It acts as a holding place for data being processed and for intermediate results during calculations.

The two types of registers used in the CPU are:

1. General Purpose Register: Used for storing data and addresses that the CPU is currently processing.
2. Special Purpose Register: Used for specific control functions within the CPU, like the program counter.

Communication protocols are defined as a set of rules that allow two electronic devices to connect and exchange data.

In simplex communication, data travels in one direction only, meaning one device sends while the other receives. In half-duplex communication, both devices can send and receive data, but not simultaneously; they take turns communicating.

The Serial Peripheral Interface (SPI) operates as a synchronous serial communication mechanism that uses separate clock and data lines for bidirectional communication. It allows multiple devices to communicate over the same bus, with a master device controlling the interaction.

Two disadvantages of SPI are:

1. Susceptibility to noise: Since SPI uses physical wires, it can be affected by electrical noise, which could corrupt data.
2. Distance constraints: SPI can only effectively communicate over short distances due to signal degradation.

The maximum cable length for RS-485 communication is 1200 meters.

The mode of operation for RS-485 is either simplex or half-duplex.

Two devices that can be connected using the RS-485 interface are:

1. Point of Sale terminals
2. CNC machines

An instruction cycle involves the CPU fetching an instruction from memory, decoding the instruction, considering all input data, and then executing that instruction. This cycle is fundamental to executing programs.

The flow chart for the monostable device involves the following steps:

1. Start
2. Check if the switch is pressed:
   • If Yes, turn the Output On.
   • Wait for 5 seconds.
   • Turn the Output Off.
   • Return to the Start.
3. If No, continuously check for the switch being pressed.