save button state for elevator

[D.A.(Tony)Stewart]

Is that mean that i should use flip flop for each floor?
as I will program it to answer the call independently.

Keep in mind you need memory storage for each floor button activity.
A FF is a memory cell no different in concept to a bit in RAM memory or a stage in a shift register.
Each are examples of binary memory cell.

Remember, define the algorithms first, and dont worry about implementation.

 

[BradtheRad]

I don't understand how the shift register can be used? i mean how to connect it hardware. it just make shifts so it can't say which floor is calling.

Brad,

You're describing a FIFO memory

Yes, I got as far as a fifo. I guess that's as far as I got.

For a shift register I picture a set of flip flops. It stores only the latest button press.

This simulation is oversimplified. It omits several details.



When you press a floor's call button, it sends its number in binary. The flip flops store it.

If you want to store all calls, then you need:

(a) several registers
(b) a means to shift stored values from one register to the next
(c) a means to send each button press to an unused shift register

It sounds very unwieldy.

 

[ads-ee]

It sounds very unwieldy.

And annoys people as it results in an elevator that will skip floors that want to go in the same direction depending on the ordering of the button presses.

A arbiter that arbitrates on reaching each floor before going to the next floor would be the best solution, two arbiters one for up and one for down motion (perhaps they could be combined, I don't know). The arbiter decides if a floor gets stopped at or not, when moving in a specific direction.

The OP should still design the control scheme and the test cases for operation before coding anything. Not sure why they have to use a shift register, but it's probably a requirement thrown in by their instructor (probably wants them to implement a shift register based round robin arbiter).