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2025-03-24 07:59本頁面
【正文】 ons: As well as I / O using the external (the internal pullup resistor), there are some special features, from a special register to set the specific features please refer to our explanation behind the pin. Internal EPROM of the microcontroller chip (for example, 8751), for the writing process required to provide specialized programming and programming pulse power, these signals are also provided in the form from the signal pin, and Namely: programming pulse: 30 feet (ALE / PROG) Programming voltage (25V): 31 feet (EA / Vpp) In introducing the four I / O port referred to a pullup resistor Then, pullup resistor is what Dongdong do? What role does he play? Said the resistance that is of course, is a resistor, when as an input, the pullup resistor pulled its potential, if the input is low you can provide a current source。s internal structure and position, we know that in 8051 within the a 4KB or 8KB of program memory (ROM), ROM39。 2, external ROM reading at each machine cycle will move twice。 4, external ROM, and ROMfootphase OE. See Figure 2 (8051 extension 2KB EEPROM circuit in Figure PSEN and expansion ROM in the OE pinphase) EA / VPP access and sequence memory control signals 1, then high time: CPU reads the internal program memory (ROM) Expansion of the external ROM: When reading the internal program memory than 0FFFH (8051) 1FFFH (8052) automatically reads the external ROM. 2, then low when: CPU to read external program memory (ROM). In the previous study, we are aware, there is no internal ROM MCU 8031, then 8031 microcontroller in the application, this pin is a low level of direct. 3,8751 Shaoxie internal EPROM, to make use of this pin input voltage of 21V for Shao Xie. RST Reset signal: when the input signal continuously high for more than two machine cycles when it is effective to plete the MCU reset initialization, when the reset program counter PC = 0000H, ie, after reset from the program memory of the 0000H unit to read the first script. External cr
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