159.253
Tutorial topic2
ASMs
[2001]
1An ASM state…
(A)May never contain more than one unconditional output
(B)Is entered into and exited from as the result of input from a separate controller implemented as a Finite State Machine.
(C)May not contain both conditional and unconditional outputs
(D)May contain more than one conditional test
[1]
[2001]
2The memory in an ASM…
(A)Calculates the next state of the ASM
(B)Loads a new state number at each clock pulse
(C)Contains the next state of the ASM
(D)Buffers the current outputs till they are needed by the external circuitry
[1]
[2000]
3Tri-state logic…
(A)was invented virtually simultaneously by researchers in California, Massachusetts and Washington (the state). Hence the name.
(B)only allows a chip to connect its output to the power supply when output-enable is true.
(C)cannot be used with bus-based architectures, because of voltage conflicts on the shared data paths.
(D)was invented virtually simultaneously by researchers in California, Massachusetts and Alabama. Hence the name.
[1]
[2000]
4In a properly designed ASM…
(A)conditional outputs are optional, conditional tests are optional, but at least one unconditional output must be made true in each state.
(B)there are no states with no outputs.
(C)all states should have a conditional test to ensure that the state following the current state is correct.
(D)successive states happen on successive clock pulses, but the ASM can occupy a single state for long periods of time.
[1]
[1996]
5 Design a circuit using the ASM methodology for controlling the closing of an electric window.
It should accept the inputs:
CLOSE true when someone requires the window to close
CLOSEDtrue when the window has closed
OBSTRUCTION true if the window encounters resistance while closing
and generate the output :
POWERwhich actuates the motor that closes the window
The window should start to close when CLOSE becomes true and stop closing when CLOSED becomes true. If an obstruction is encountered, the closing should pause until the obstruction goes away.
[15]
[1995]
6Write down five principles of the ASM design methodology.
NOTE: Your principles should NOT describe the graphic conventions which are used in ASM diagram.
They SHOULD describe the purpose of ASMs and a general outline of how the circuits are constructed
[5]
[1995]
7(a) Design divide-by-three circuit using an ASM. Its output should be true on one of every three clock cycles.
[5]
(b) Correct each of the following ASM diagrams, or if correction is not possible, indicate what the error is.
(i)
[1]
(ii)
[1]
(iii)
[1]
(iv)
[1]
(v)
[1]