P89LPC935 Microcontroller Tutorial - gmitWEB
P89LPC935 Microcontroller Tutorial - gmitWEB
P89LPC935 Microcontroller Tutorial - gmitWEB
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Port Configurations<br />
• Input Only<br />
– This is the default configuration at reset<br />
• Quasi-bidirectional<br />
– Standard 80C51 outputs<br />
– Strong pull-down can sink 20mA when output = ‘0’<br />
– Weak pull-up can source 20uA when output = ‘1’<br />
– Can be used to interface to TTL devices<br />
• Push-Pull<br />
– Used when more source current is required<br />
• Can source 3.2mA when outputting a ‘1’<br />
– Strong pull-down can sink 20mA when output = ‘0’<br />
• Open Drain<br />
– Needs an external pull-up to output a logic ‘1’<br />
– Best solution when interfacing to 5V circuits<br />
Diploma Project <strong>Tutorial</strong> 12
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