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Electronics => Electronics => Topic started by: unicoder on May 09, 2009, 10:20:12 AM

Title: What does the word 'drive' or 'driver' mean?
Post by: unicoder on May 09, 2009, 10:20:12 AM

I was wondering about the Max232 IC and was wondering:
If a chip says it can 'drive' RS232 circuits does it need the 5v to 12v conversion that a Max232 IC provides?


*EDIT* Port three stated as supporting 8051 features and able to drive LS TTL
To expound the datasheet says
"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 data sheet)
because of the internal pullups."


If this means I won't have to use a Max232 IC then thats good. Otherwise I will have to see about fabricating one.

Title: Re: What does the word 'drive' or 'driver' mean?
Post by: colorclocks on May 10, 2009, 03:02:06 PM

You should use the Max232 driver.  RS-232 signals are >+3V and <-3V.  The 8051 is a TTL output, which can drive a load to >+3V, but can't drive it to <-3V, so it's not going to be heard by an RS-232 receiver.  Also, RS-232 drivers are handy because they usually can take a dead short without frying.  I doubt the 8051 outputs are so forgiving.

Another reason to use a driver is to defend the 8051 against accidental overvoltage.

Title: Re: What does the word 'drive' or 'driver' mean?
Post by: unicoder on May 10, 2009, 08:52:37 PM

Ah good suggestion. I ended up throwing my on circuit together that did what a Max232 does (tosome degree and enough effect)