(Registers/Counters) - What is the final contents of the register?

[kuranme]

The contents of a 8-bit register is initially 01110111. The register is shifted right six times with the serial input being 011001. The same register is then shifted left 4 times with the serial input being 0101. What is the final contents of the register?

 

[picbits]

Show us your working out so far .......

 

[Pommie]

What does "serial input" mean?

Mike.

 

[NsrMagazin]

Serial means that you give 1 bit to the register per 1 clock cycle (1 shift).

 

[Pommie]

Serial means that you give 1 bit to the register per 1 clock cycle (1 shift).

I know what serial means or rather, I assumed that's what it meant. However the answer is dependant on if it's MSB or LSB first. There is also a third possibility - the bits are shifted the same way as the register. So, three possible answers due to an incomplete question.

Mike.

 

[NsrMagazin]

Does not matters. You always shift the LSB first into the MSB of the register.

 

[Pommie]

Does not matters. You always shift the LSB first into the MSB of the register.

What about when shifting left?

Mike.

 

[NsrMagazin]

Normally there is only 1 input, you can not shift with 2 inputs unless the register is designed for it.

If there is 1 input:
Shifting to the left clears the LSB bits being shifted and shifts the rest to the left.

If you want to shift with 2 inputs, that means that you have to supply the bits from the other end in which case the result is clear. However this requirement is not mentioned and ambiguous.

 

[Pommie]

Ahah, we finally agree. It's an ambiguous question. As a computer programmer since the 70s I should be able to answer these type of questions but teachers keep asking incomplete questions.

Mike.