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Design Aware Gate Array Style Spare Latch Planning and Distribution

IP.com Disclosure Number: IPCOM000241528D
Publication Date: 2015-May-08
Document File: 6 page(s) / 175K

Publishing Venue

The IP.com Prior Art Database

Abstract

The method described here covers alternative usage model for spare latch as a part of ECO planning process. Spare Latches are used like GA Cells instead of hard-coded spare latch count in RTL. This will lead to potential power savings as these cells will not burn any power unless used for an ECO. Also, spare-latch count can be increased as cost of these resources is much lower.

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Design Aware Gate Array Style Spare Latch Planning and Distribution

Design Aware Gate Array Style Spare Latch Planning and Distribution

Spare latches are special cells which are used and distributed in Design to meet Engineering Change Order (ECO) requirements that involves new sequential device (latch) connection as a part of ECO. Unlike Gate Array (GA) cells (used for combinational device requirements towards ECO implementation) which are used on-the-fly based on ECO needs, Spare latch distribution is "hardened" during regular implementation itself. The problem with this "always connected" approach is higher power consumption (both dynamic and leakage), clock loading issues and unable to provide higher number of spare latches if needed. Hence, under current scheme of things, efficient and optimal Spare Latch distribution is often sub-optimal and some enhancements are possible.

The method described here covers alternative usage model for spare latch as a part of ECO planning process. Spare Latches are used like GA Cells instead of hard-coded spare latch count in RTL. Spare latch countis determined using a composite function per regionfactoring in parameters like latch count, slack, routability e.t.c. Spare Latch Distributionis performed keeping in mind that not all LCBs are typically fully loaded in any given region of the design, use under-driven LCBs as anchor points for spare latches (wherever possible). Also, spare latches are placed with the proximity and capacitance load limit awareness of regular under-driven LCBs present in vicinity (per region). This will lead to potential power savings as these cells will not burn any power unless used for an ECO. Also, spare-latch count can be increased as cost of these resources is much lower.

ECO planning is a important methodology as a part of overall SOC Physical realization. ECO planning involves allocation of resources for both combinational and sequential components of design in the likelihood of an ECO. Also, these resources need to be well distributed to have better accessibility from all parts of the design.

In current ECO planning approach, finite number of spare latches is used to meet demands of sequential component requirements during ECO time. Because of area and power overhead of spare latches, it cannot be used in abundance. Illustration of current spare latch distribution is depicted in Figure 1.

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Figure-1: Illustration of current ECO planning scheme

In contrast to current approach, proposed embodiments show how to perform ECO planning with spare latch resources not connected to power grid network.

In current approach, Spare latch is originally un- connected to anchor LCB and power supply, so it is not burning leakage as well as dynamic power. In "always connected" mode, spare latch count is limited because increase in latch count will increase power consumption and routability overhead. In "unconnected unless required" mode, spare latch count can be...