89C51 means it has FLASH | Microcontroller › 8051 › reg51.h › 89C51 means it has FLASH January 29, 2015 at 9:45 am #12547 Ashutosh BhattParticipant 89C51 means it has FLASH memory inside. 80C51 means ROM inside. this is the difference if KEIL you can use reg51.h for entire family of MCS51 like 89C52/89S52/89C4051/89C2051 etc all
