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. It includes components such as the CPU, ROM, RAM, and I/O interfaces.

(a) The control bus is used mainly for the CPU to issue control instructions to both memory and associated input/output ports. (b) The data bus functions as the 'highway' through which data is transferred between the CPU, memory, and all input and output ports.

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

Once data enters the Current Instruction Register (CIR) from the Memory Data Register (MDR), it is decoded by the control unit for execution. The instruction indicates what operation is to be performed, along with the address of the data needed to execute that instruction.

The accumulator serves as a storage location that temporarily holds data required for arithmetic operations, enabling the CPU to perform calculations efficiently.

The two types of registers used within the CPU are:

1. General purpose registers: These are used for temporary data storage during program execution.
2. Special purpose registers: These include specific registers like the program counter (PC) and instruction register (IR), which have designated roles in processing.

A communication protocol refers to a set of rules that dictate how two electronic devices communicate and exchange data.

In simplex communication, data travels in only one direction, from the transmitter to the receiver. In contrast, half-duplex communication allows data to flow in both directions, but not simultaneously, which means one device sends while the other receives.

The serial peripheral interface (SPI) operates as a synchronous serial communication link that facilitates data exchange in both directions. It utilizes separate lines for data transmission and reception, allowing devices to share information effectively.

The disadvantages of SPI include:

1. Susceptibility to noise: The signal integrity can be compromised, particularly over longer distances.
2. Distance limitations: SPI communication can only travel relatively short distances effectively.

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

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

Devices that can utilize the RS-485 interface include:

1. Point of Sale Terminals: Used in retail environments for transaction processing.
2. CNC Machines: Utilized in manufacturing for precise control of machinery.

During an instruction cycle, the CPU fetches a program instruction from its memory, decodes the instruction, assesses all relevant inputs, and then executes the instruction accordingly.

The complete flow chart for the monostable device should illustrate the state changes upon triggering input. Start with 'Start', check 'Switch pressed?'. If yes, proceed to 'Output On', then 'Wait 5 seconds', followed by 'Output Off' before returning to the start.