when a microcontroller communicates with another one via one of the communication protocols there is a configuration bit in a control register to choose whether to send(write) or receive(read) this bit in all the communication protocols that I dealt with is configured by setting it to "1" for reading and clearing it for writing..why is that?
closed as primarily opinion-based by Chris Stratton, laptop2d, RoyC, mkeith, Bimpelrekkie Apr 10 at 7:40
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Reading is a more benign state than writing.
Back in days of transistor/transistor/logic (TTL), a logic "high" was a default state for a logic input: if nothing is connected to a TTL logic input, it floats to logic high - you had to add current to pull it to logic "low". In such a logic world, it would make sense to choose the default logic state of "high" to correspond to the benign state of "reading".
These days of CMOS logic have no default logic state: an input could equally float to logic "low" as it could float to logic "high".
So the answer may be - a choice standardized through legacy.
The same argument applies to the logic choice of chip select ...logic high is again the default un-selected, benign logic state, while logic low activates the chip's input/output structure.