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What is the output current from a 8051 micro controller anyone of port pin?
Wiki User
∙ 11y ago
An 8051 is unlike most modern processors in that the ports are essentially open-collector drivers. Some of the ports (1, 2, and 3) have internal pull-ups, but these are usually quite weak (500 micro-amps or less); port 0 has no pull-ups at all. When the chip is reset, 1s are stored in all port bits. When a 0 is written to a port pin, it is pulled down to ground, with a current rating that varies widely depending upon the specific variant. The original Intel 8051H could only sink about 7 mA (4 TTL loads), but most chips now will sink 15-20 with no problems - enough to light an LED.
Another way of thinking about this is that, upon reset, the port pins are all 1s. Because of the weak or no pull-ups, they can be used as inputs. The only output state for a port is low, so if an external load needs to be driven, it must be a "sinking" type of load.
Wiki User
∙ 11y ago
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Give difference between micro controller and micro processor in terms of architecture?
no answer
