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Using P0 port for driving +3.3 V Devices

Narasimha Swamy
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Hello,

I have a question. Can we use P0 port of 8051 for I/O of an external device which has +3.3V ratings for its I/O?

Thanks

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    I have a question. Don't you think it would be relevant to specify exactly what 8051 chip you have, since there are thousands and thousands of different manufacturers and models available?

    In the general case, the answer is no. But the datasheet for your specific chip can tell you what voltage levels the pin inputs requires to be safely detected as high or low. And the datasheet for your 3.3V device will tell what voltages it emits as high or low.

    In the other direction, where the 8051 pin is output, it depends a lot on if your specific chip have a pseudo output with a pull-up to 3.3V or if it forcibly drives the signal to +5V. And it depends a lot on if the external hardware is 5V tolerant - some 3.3V chips have 5V-tolerant inputs, i.e. output signals swings between 0 an 3.3V while inputs are detected as low or high in the 3.3V range but allowed to be drawn to 5V without problems.

    Without more information from you, we can't really help you but tell you to read the datasheets. You might have to add resistors or level converters between the two chips. But your didn't even spent the time to tell your signal directions.

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  • 0 Offline

    I have a question. Don't you think it would be relevant to specify exactly what 8051 chip you have, since there are thousands and thousands of different manufacturers and models available?

    In the general case, the answer is no. But the datasheet for your specific chip can tell you what voltage levels the pin inputs requires to be safely detected as high or low. And the datasheet for your 3.3V device will tell what voltages it emits as high or low.

    In the other direction, where the 8051 pin is output, it depends a lot on if your specific chip have a pseudo output with a pull-up to 3.3V or if it forcibly drives the signal to +5V. And it depends a lot on if the external hardware is 5V tolerant - some 3.3V chips have 5V-tolerant inputs, i.e. output signals swings between 0 an 3.3V while inputs are detected as low or high in the 3.3V range but allowed to be drawn to 5V without problems.

    Without more information from you, we can't really help you but tell you to read the datasheets. You might have to add resistors or level converters between the two chips. But your didn't even spent the time to tell your signal directions.

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