A protocol analyzer typically captures traffic pertaining to a specific protocol for later analysis this task is usually carried out without effecting or disturbing the original system under analysis.
While an emulator/exerciser typically refers to a device designed to emulate a particular microcontroller, microprocessor or a peripheral device attached to a particular bus protocol like I2C, SPI, RS-232, etc.
Emulators for microcontrollers or microprocessors are typically referred to as In-Circuit Emulators (ICE) and offer a more comprehensive list of features for debugging methods combined with trace capture and analysis.
Emulators for a particular bus protocol can typically emulate a specific peripheral device through the means of scripts and other programmatic methods.
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