NANOSCALE STANDARD DIGITAL MODULES - Bio-Inspired and Nanoscale Integrated Computing - page 252

Analog
select
input

Select inputs Data inputs Output

s k − 1
2 K − 1

s k − 2 x N − 1

s 0 S x 0 x 1 x 2

Y

x 0

... ...

1

2 K − 2

f sel f out

f adc 1

y

x i

f i

2

Digital to analog
converter

Multiplexer

x N − 1

...

S k − 1 S 0

Figure 9.7. Structure of a nanoscale spin-wave multiplexer.

We present two different methods for implementing a nanoscale spin-wave
multiplexer, in which input and output nodes intercommunicate via a spin-wave
bus, as shown in Figure 9.7. Similar to the implementation of the binary decoder,
in both designs, the binary select-inputs value is first converted to analog using a
digital to analog converter.
In the first method of implementing a multiplexer, the analog-select-input
node broadcasts on frequency f sel , the index number of the input it is selecting. The
data-input nodes, which are tuned on f sel , receive the broadcasted value, compare
it to their indices, and check if they have been selected. The selected data-input
node sends its data on f out that is the frequency the output node's receiver is tuned
on. Table 9.7 shows the sending and receiving frequency assignment of the nodes.
In the second method, a distinct frequency is assigned to each data-input
node. In other words, data input i is tuned on f i . Assuming that the analog-select-
input node contains the index i, it broadcasts a signal on f i to be received by the ith
data-input node. Upon receiving a signal, this node sends its data on the frequency
at which the output node is tuned. Thus, the output node receives the data sent by
the selected data-input node. Table 9.8 shows the frequency assignments for the
second method of implementing a spin-wave multiplexer.
Multiplexers are widely used in various digital circuits. As an example, we
mention one of their applications in digital signal processing. The multiplexer
takes several separate digital data streams and combines them together into one
data stream of a higher data rate. This allows multiple data streams to be carried
from one place to another over one physical link.

TABLE 9 . 7 . Frequency Assignments in the First Method of
Multiplexer Implementation
Node

Sending frequency Receiving frequency

Binary select inputs f adc -

Analog select input f sel f adc

Data inputs f out f sel

Output - f out