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EE2354 – MICROPROCESSORS AND MICROCONTROLLER Single
instruction, which clears the most significant bit of B register of 8051, without
affecting the remaining bits, is CLR B.
6. Explain the function of the pins PSEN and EA of 8051. PSEN: PSEN stands for program store enable. In 8051 based system in which an external
ROM holds the program code, this pin is connected to the OE pin of the ROM. EA EA stands for external access. When
the EA pin is connected to Vcc, program fetched to address H through 0FFFH are directed to the internal ROM and program fetches to addresses H through FFFFH are directed to external ROM/EPROM.
When the EA pin is grounded, all addresses fetched by program are directed to the external ROM/EPROM.
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