Glossary of Key Terms
Glossary of Key Terms
| Term | Definition |
| Actuator | Compares the output given by a D-A Converter to the actual (expected) output stored in it and stores the approved output. |
| Address Latch Enable (ALE) | An active-high output pin used, especially for the 8031 IC, to decide whether the P0 pins are being used as an Address bus (ALE=0) or a Data bus (ALE=1). |
| Addressing Mode | Refers to how you are addressing a given memory location. The 8051 has five modes: Immediate, Direct, Register Direct, Register Indirect, and Indexed. |
| Assembler | A program that takes basic computer instructions (assembly language) and converts them into a pattern of bits (object code) that the computer’s processor can use. |
| Compiler | A computer program that transforms source code written in a programming language into another computer language, most commonly to create an executable program. |
| Counter | A device that stores the number of times a particular event or process has occurred with respect to a clock signal. It is used to count events happening outside the microcontroller. |
| Cross-Compiler | A compiler that can create a program that runs on a computer with a different CPU or operating system than the computer on which the compiler compiled the program. |
| CISC (Complex Instruction Set Computer) | A computer that can address a large number of instructions. |
| Decompiler | A program that can translate a program from a low-level language to a high-level language. |
| Directive (Pseudo-instruction) | A statement in an assembly language program that gives instructions to the assembler, but does not generate machine code for the CPU. Examples include ORG and END. |
| Embedded System | A microcontroller or microprocessor-based system which is designed to perform a specific task. It can be thought of as a computer hardware system having software embedded in it. |
| Emulator | A hardware kit, software program, or both, which imitates the functions of one computer system (the guest) in another computer system (the host). |
| Harvard Architecture | An architecture that offers separate storage and signal buses for instructions and data, allowing for simultaneous access to both. |
| Instruction | A statement in an assembly language program that tells the CPU what to do. Instructions are translated into machine code for the CPU to execute. |
| Interrupt | A signal to the processor emitted by hardware or software indicating an event that needs immediate attention, causing the processor to execute an Interrupt Service Routine. |
| Interrupt Service Routine (ISR) | Also called an interrupt handler, it is a routine that tells the processor or controller what to do when a specific interrupt occurs. |
| Interrupt Vector Table | A table of memory locations set aside to hold the addresses of ISRs. |
| Little Endian / Big Endian | Two methods of storing multi-byte data in memory. Big-Endian stores the most significant byte at the lowest memory address, while Little-Endian stores the least significant byte at the lowest memory address. |
| Microcontroller | A single-chip VLSI unit (also called a microcomputer) that possesses enhanced input/output capability and a number of on-chip functional units like RAM, ROM, I/O ports, and timers. |
| Microprocessor | A single VLSI chip having a CPU, and potentially other units like caches and floating point processing units that help in faster processing of instructions. |
| Mnemonics | Symbols provided by assembly languages to represent machine-level code instructions, such as ADD and MOV. |
| Polling | The state of continuous monitoring, where a microcontroller keeps checking the status of other devices, consuming all its processing time for monitoring. |
| Program Counter (PC) | A 16-bit or 32-bit register that contains the address of the next instruction to be executed. It is a 2-byte register in the 8051. |
| Program Status Word (PSW) | An 8-bit register, also known as the flag register, that contains status bits that reflect the current status of the CPU. |
| Real Time Operating System (RTOS) | A component of an embedded system that supervises the application software and provides a mechanism to let the processor run a process as per scheduling to control latencies. |
| Register | A component used in the CPU to temporarily store information, which could be data to be processed or an address pointing to data to be fetched. |
| RISC (Reduced Instruction Set Computer) | Computers that use fewer instructions with simple constructs so they can be executed much faster within the CPU without having to use memory. |
| Sensor | A device that measures a physical quantity and converts it to an electrical signal which can be read by an observer or an electronic instrument. |
| Simulator | A debugging tool that tries to model the behavior of a complete microcontroller in software on a host computer. |
| Special Function Register (SFR) | A register within a microprocessor that controls or monitors various functions of the microprocessor. They are located in the address range of 80H to FFH in the 8051. |
| Stack | A section of RAM used by the CPU to temporarily store information, such as data or a memory address. |
| Stack Pointer (SP) | An 8-bit CPU register used to access the stack. It points to the location from where the next value is to be removed from the stack. |
| System | An arrangement in which all its units assemble and work together according to a set of rules. |
| Timer | A specialized type of clock used to measure time intervals. In the 8051, it uses the frequency of the internal clock to generate delays. |
| Von Neumann Architecture | An architecture where one data path or bus exists for both instruction and data, preventing simultaneous access. |