Embedded System Terminology - R
| Race Condition - A situation in which the combined effects of two or more programmatic threads (or a single thread and an ISR) varies depending on the precise order in which the instructions of each are executed. |
| Random Access Memory (RAM) - Volatile memory in which any location within it can be accessed directly (randomly, rather than sequentially from some starting point), and whose content can be changed more than once (the number depending on the hardware). |
| Rate Monotonic Analysis - The process of analyzing a real-time system to assign individual thread priorities according to the rate monotonic algorithm. |
| Read Only Memory (ROM) - A type of non-volatile memory that can be used to store data on an embedded system permanently. |
| Rectifier - An electronic component that allows current to flow in only one direction. |
| Reduced Instruction Set Computer (RISC) - An ISA that usually defines simpler operations made up of fewer instructions. |
| Register - A combination of various flip-flops that can be used to temporarily store data or delay signals. |
| Relay - An electromagnetic switch. There are many types of relays, including the DPDT (Double Pole Double Throw) relay which contains two contacts that can be toggled both ways (on and OFF), a DPST (Double Pole Single Throw) relay which contains two contacts that can only be switched on or off, a SPDT (Single Pole Double Throw) relay which contains one contact that can be toggled both ways (on and off), and a SPST (Single Pole Single Throw) relay which contains one set of contacts and can only be switched one way (on or off). |
| Resistor - An electronic device made up of conductive materials that have had their conductivity altered in some fashion in order to allow for an increase in resistance. |
| Real Time Operating System (RTOS) - An OS in which tasks meet their deadlines, and related execution times are predictable (deterministic). |
| Real time system - Any computer system, embedded or otherwise, that has timeliness requirements. |
| Recursive - Said of software that calls itself. Recursion should generally be avoided in an embedded system, since it frequently requires a large stack. |
| Reentrant - Said of software that can be executed multiple times simultaneously. A reentrant function can be safely called recursively or from multiple tasks. The key to making code reentrant is to ensure mutual exclusion whenever accessing global variables or shared registers |
| Relocatable - A file containing object code that is almost ready for execution on the target. The final remaining step is to use a locator or loader to fix the remaining relocatable addresses within the code. The result of that process is an executable. |
| Reset Address - The address from which the first instruction will be fetched after a processor is powered on or reset; usually in ROM |
| Reset Code - A small piece of code that is placed at the reset address. The reset code is usually written in assembly language and might simply be the equivalent of "jump to the startup code." |
| Reset Vector - See Reset address |
| ROM emulator - A debugging tool that plugs into the target system's ROM sockets |
| Romizer - A device used to write data to EPROMs. |
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Related topics:
Embedded System Architecture | Embedded Hardware Architecture | Embedded Software Architecture | Embedded Software Definition | Embedded System Acronyms | Embedded System Symbols
List of topics: Embedded System
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