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【文章內(nèi)容簡介】 lse. PORG pulse input for the program: In the fifth lesson MCU39。s internal structure and position, we know that in 8051 within the a 4KB or 8KB of program memory (ROM), ROM39。s role is to be used to store user needs implementation of the program, then we are into how to write good programs into this ROM in it? Is actually programmed into the pulse input can be written, this pulse input port is PROG. PSEN external program memory read strobe: In reading an external ROM, PSEN low effective, in order to achieve an external ROM module read. 1, the internal ROM reading, PSEN is not action。 2, external ROM reading at each machine cycle will move twice。 3, external RAM read, the two PSEN pulse is skipped will not be output。 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 crystal oscillator pins XTAL1 and XTAL2. When using the chip internal clock, this twopin for external quartz crystal and finetuning capacitor。 when using an external clock, used to access an external clock pulse signal. VCC: Power Supply +5 V input VSS: GND Ground. AVR and the pic are
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