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AP83C51FA Datasheet(PDF) 5 Page - Intel Corporation |
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AP83C51FA Datasheet(HTML) 5 Page - Intel Corporation |
5 / 13 page AUTOMOTIVE 80C51FA83C51FA addresses (MOVX Ri) Port 2 emits the contents of the P2 Special Function Register Port 3 Port 3 is an 8-bit bidirectional IO port with internal pullups The Port 3 output buffers can drive LS TTL inputs Port 3 pins that have 1’s written to them are pulled high by the internal pullups and in that state can be used as inputs As inputs Port 3 pins that are externally pulled low will source current (IIL on the datasheet) because of the pullups Port 3 also serves the functions of various special features of the MCS 51 microcontroller family as listed below Port Pin Alternate Function P30 RXD (serial input port) P31 TXD (serial output port) P32 INT0 (external interrupt 0) P33 INT1 (external interrupt 1) P34 T0 (Timer 0 external input) P35 T1 (Timer 1 external input) P36 WR (external data memory write strobe) P37 RD (external data memory read strobe) RESET Reset input A high on this pin for two ma- chine cycles while the oscillator is running resets the device An internal pulldown resistor permits a pow- er-on reset with only a capacitor connected to VCC ALEPROG Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory In normal operation ALE is emitted at a constant rate of the oscillator frequency and may be used for external timing or clocking purposes Note how- ever that one ALE pulse is skipped during each ac- cess to external Data Memory Throughout the remainder of this datasheet ALE will refer to the signal coming out of the ALEPROG pin and the pin will be referred to as the ALEPROG pin PSEN Program Store Enable is the read strobe to external Program Memory When the 83C51FA is executing code from external Program Memory PSEN is activated twice each ma- chine cycle except that two PSEN activations are skipped during each access to external Data Memo- ry EA VPP External Access enable EA must be strapped to VSS in order to enable the device to fetch code from external Program Memory locations 0000H to 0FFFFH Note however that if either of the Program Lock bits are programmed EA will be internally latched on reset EA should be strapped to VCC for internal program executions XTAL1 Input to the inverting oscillator amplifier XTAL2 Output from the inverting oscillator amplifi- er OSCILLATOR CHARACTERISTICS XTAL1 and XTAL2 are the input and output respec- tively of a inverting amplifier which can be config- ured for use as an on-chip oscillator as shown in Figure 4 Either a quartz crystal or ceramic resonator may be used More detailed information concerning the use of the on-chip oscillator is available in Appli- cation Note AP-155 ‘‘Oscillators for Microcontrol- lers’’ To drive the device from an external clock source XTAL1 should be driven while XTAL2 floats as shown in Figure 5 There are no requirements on the duty cycle of the external clock signal since the in- put to the internal clocking circuitry is through a di- vide-by-two flip-flop but minimum and maximum high and low times specified on the datasheet must be observed An external oscillator may encounter as much as a 100 pF load at XTAL1 when it starts up This is due to interaction between the amplifier and its feedback capacitance Once the external signal meets the VIL and VIH specifications the capacitance will not ex- ceed 20 pF 270501 – 5 C1 C2 e 30 pF g10 pF for Crystals For Ceramic Resonators contact resonator manufacturer Figure 4 Oscillator Connections 5 |
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