8051-Compatible µCs Map Their Flash Into Two Banks

Representing the firm's first foray into the 8051 microcontroller mart, the FlashFlex51 family of MCUs employs an embedded flash memory array mapped into primary and secondary banks and uses a small size sector for both code and data storage. The dual memory bank architecture results in an In-Application Programming (IAP) mode that allows the CPU to run user programs from one bank while concurrently servicing a flash programming operation in the background on the other bank. SST89C54, SST89C58 and SST89C59, the first three members of the FlashFlex51 family, embed 20, 36 and 68 Kbytes of NOR-type SuperFlash EEPROM, respectively. The MCUs' primary memory bank of 16, 32 and 64 Kbytes, with a 128-byte sector size, occupies the internal ROM space for an 8051-compatible µC. The secondary, 4-Kbyte bank with a 64-byte sector size can be used for either electronically erasable data storage or code storage. Other features of the new MCUs include 256 bytes register/data RAM, three 16-bit timer/counters, programmable UART, configurable watch-dog timer, and more. 'C54, 'C58 and 'C59 MCUs are available in 40-pin PDIPs and 44-pin PLCCs and TQFPs.