Pass Transistor Logic (PTL) is a well known approach for implementing digital circuits.
In order to handle larger designs and also to ensure that the total number of series
devices in the resulting circuit is bounded, partitioned Reduced Ordered Binary Decision
Diagrams (ROBDDs) can be used to generate the PTL circuit. The output signals of each
partitioned block typically needs to be buffered. In this thesis, a new methodology is presented
to perform generalized buffering of the outputs of PTL blocks. By performing the
Boolean division of each PTL block using different gates in a library, we select the gate
that results in the largest reduction in the height of the PTL block. In this manner, these
gates serve the function of buffering the outputs of the PTL blocks, while also reducing the
height and delay of the PTL block.
PTL synthesis with generalized buffering was implemented in two different ways. In
the first approach, Boolean division was used to perform generalized buffering. In the second
approach, compatible observability don't cares (CODCs) were utilized in tandem with
Boolean division to simplify the ROBDDs and to reduce the logic in PTL structure. Also
CODCs were computed in two different manners: one using full simplify to compute
complete CODCs and another using, approximate CODCs (ACODCs).
Over a number of examples, on an average, generalized buffering without CODCs
results in a 24% reduction in delay, and a 3% improvement in circuit area, compared to
a traditional buffered PTL implementation. When ACODCs were used, the delay was reduced by 29%, and the total area was reduced by 5% compared to traditional buffering.
With complete CODCs, the delay and area reduction compared to traditional buffering
was 28% and 6% respectively. Therefore, results show that generalized buffering provides
better implementation of the circuits than the traditional buffering method.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/5906 |
| Date | 17 September 2007 |
| Creators | Garg, Rajesh |
| Contributors | Khatri, Sunil P. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 260183 bytes, electronic, application/pdf, born digital |
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