NANOSCALE STANDARD DIGITAL MODULES - Bio-Inspired and Nanoscale Integrated Computing - page 258

Inputs

Outputs

Shift register
control

... ...

y n − 1 y i y 0

p k − 1 p k − 2 p 0 x n+p − 1 x n x n − 1 x i x 0 x − 1 x

− p

... ... ... ... ...

1

Shift right
Shift left

P

f i+d f i − d

Digital to analog
converter

Figure 9.12. Structure of a nanoscale spin-wave p-shifter with overlapping input/
output nodes.

input with value 1, the priority encoder may have several 1-valued inputs. The
output represents the index of the highest priority input having the value 1. The
priority is a fixed ordering implemented by the encoder; usually, x N 1 has
the highest priority, whereas x 0 has the lowest [1].
The general way to implement a priority encoder is to have a module called
''priority resolution'' which keeps the highest priority 1 and sets all the other
inputs to 0. These data will be the input to a standard binary encoder which gives
the index of the only input with value 1. In implementing the spin-wave priority
encoder, however, we do not use a ''priority resolution'' module to reset the lower
priority 1-valued inputs to 0. Instead, we use spin-wave switches to force the waves
in the desired direction and arrange the nodes in a fashion that the output node
receives the index of the highest priority 1-valued input.
The structure of a spin-wave priority encoder is shown in Figure 9.13. In this
design, the highest priority node, x N 1 , is placed closest to the output node, while
the lowest priority node, x 0 , the farthest. Note that in the structure shown in

y k − 1 y 0

...

Binary outputs:

N = 2 K Input A/D

x 0

y 0

Analog
out

x 0 x 1 x i x N − 1

... ...

y i

x i

i

y k − 1

x N − 1

Spin-wave switch Spin-wave bus

Figure 9.13. Structure of a nanoscale spin-wave priority encoder.