Schematic:
5V power | supply | - R| |100 ohm | |0.5W - | | ------- | VDD |PIC16C84 | | | | | MCLR|------- TxD (2) | | | | +--- DTR (20) | | | | RB7 |---+--- CTS (5) | | | RB6 |------- RTS (4) | | | | To serial | GND | interface ------- | +---------- GND (7) | | power 0V supplyThe build in clamp diodes limits the input voltage, but when using the clamp diodes may the PIC16C84 latch up. Resistor R minimizes risc of latch up. And it also protect the PIC16C84 against too high currents inside which minimalize latch-up possibility.
The RS232 outputs is current limited, and it do typical not exceed +/- 15mA. PIC's handle up to +/- 20mA. Current in the clamping diodes may cause latch
up and to prevent this effect do we need the resistor R to reduce the
current from power supply. The typical current is about 3 to 4 mA, and the
voltage drop on 0.4V is ok. The maximum current is 50mA, as also
protect the PIC if it is wrong inserted.
Download PIP-02 beta driver, JDM84V31.ZIP (5K).
Download PIC16C84 utilities, PGM84V28.ZIP (25K).
Download utilities, PICUTIL3.ZIP (46K).
The utilities is inclusive source.
Extra lowcost for PIC16C84 only.
Simple programmer for PIC16C84 and 24Cxx only.
Z80 trick: Use RESET, NMI and CLOCK to bootload a romless system (RAM only).
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