Atmel AT89C51SND1 - Manual (Page 4)

Introduction
AT89C51SND1 Reference Design User Guide 1-2
4207B–MP3–04/07
1.2 Abbreviations AT89C51SND1: the MP3 microcontroller
ISP: In-System Programming
MP3: MPEG layer 3, a standard music format
PC: Personal Computer
USB: Universal Serial Bus