The 89C51/89C52/89C54/89C58 contain a non-volatile FLASH program memory that is parallel programmable. For devices that are serial programmable (In-System Programmable (ISP) and In-Application Programmable (IAP) with a boot loader), see the 89C51Rx2 or 89C66x datasheets.

All three families are Single-Chip 8-bit Microcontrollers manufactured in advanced CMOS process and are derivatives of the 80C51 microcontroller family. All the devices have the same instruction set as the 80C51.