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Handling Dot Blocks During Logic Partitioning

IP.com Disclosure Number: IPCOM000079093D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Giannuzzi, RJ: AUTHOR [+3]

Abstract

In some logic circuit families, the outputs of a subset of blocks can be physically tied together (e.g., soldered) to form a logical OR. This is called dotting. In the design automation process, this type of occurrence often is represented by a logic block called a DOT. When the logic technology permits dotting between packaging levels (e.g., chip-to-chip), problems arise in the partitioning process. The diagrams of Fig. 1 illustrate this, and a sound solution is given. In (a) is shown a subset of logic in which the outputs 1, 2 and 3 are dotted and result in inputs to block 5, a DOT. If blocks 1 and 5 are selected for a partition without blocks 2 and 3, (b) results, and the I/O (input-output) count is 4. This is erroneous since the DOT is actually just a junction.

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Handling Dot Blocks During Logic Partitioning

In some logic circuit families, the outputs of a subset of blocks can be physically tied together (e.g., soldered) to form a logical OR. This is called dotting. In the design automation process, this type of occurrence often is represented by a logic block called a DOT. When the logic technology permits dotting between packaging levels (e.g., chip-to-chip), problems arise in the partitioning process. The diagrams of Fig. 1 illustrate this, and a sound solution is given. In (a) is shown a subset of logic in which the outputs 1, 2 and 3 are dotted and result in inputs to block 5, a DOT. If blocks 1 and 5 are selected for a partition without blocks 2 and 3, (b) results, and the I/O (input-output) count is 4. This is erroneous since the DOT is actually just a junction.

The following algorithm handles the situation properly. Whenever a block whose output connecting to the input of a DOT is brought into a partition, also bring in that DOT (if not as yet in the partition) and convert other inputs to the DOT from blocks which are external to the partition to co-sinks of the DOT output. Fig. 1 (c) is the result of applying the algorithm, and here the I/O count is 2 which is correct. Note that redundant allocation of a DOT causes no inaccuracy in weighted factors such as circuit count, power, etc.

Another way of achieving proper I/O count is to just delete the inputs to the DOT which are from sources external to the partition....