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Volume 27 (Sep 30, 2004)
The Challenges and Passion Behind the Creation of the V850 Series (2/2)
Part 3: The Development of an IP Core for System LSI Chips
Realizing the ideal collaborative effort
With microcontroller application systems, components other than those used for ordinary microcontrollers are operated in line with the reference clock supplied by the microcontroller. On the contrary, for an ASIC with a built-in CPU, the CPU core (a microcontroller that has been converted to IP) as well as other components must be operated based on the same clock.
The project got off to its true start when the two teams discovered and began to understand their respective differences. Once that happened, team members were able to bridge their differences using the spec regulation process and the concept for design. For example, the most fundamental difference was in relation to reference clocks. Although the reference clock for a microcontroller application system is asynchronous with the input source clock of the microcontroller, it is synchronous with the input source clock of the ASIC IP core (Figure 1). For microcontroller application systems, the microcontroller supplies the reference clock and the other components are operated in line with the microcontroller's supply clock. However, due to the fact that the ASIC world is one of synchronicity, the microcontroller must operate in sync with the ASIC source clock in the same manner as the other components if it is to act as a CPU core. Moreover, it is necessary to carry out design changes for microcontroller application systems so as to transform board-level signal buses into silicon-level signal buses. This is because in the ASIC realm, in which it is possible to freely make connections on the same silicon, it is unnecessary to create a structure like that of a microcontroller with which various signals can be passed through a single signal bus. Although various issues were brought to light, they were steadily resolved one by one. With every issue that arose, the two teams would work together early on to develop countermeasures. The engineers on the customer side participated in the project as comrades, shared their thoughts and at times provided valuable advice that led to the resolution of problems. It can be said that this was a project in which ideal collaboration was achieved among three parties-the microcontroller team, the ASIC team and the customer.
As a system LSI core and a multipurpose product
In October 1996, Okuda and Sakurai held a review meeting with the customer after successfully completing delivery of the product. This meeting was a rather large one, with a total of 31 participants: 8 from the customer side and 23 from the NEC Electronics side. Since user logic would be included, verification by the customer was necessary. Numerous issues were raised including the need to clarify the areas of responsibility of both the customer and NEC Electronics, the imperativeness of understanding the customer's system in its entirety, and how essential it would be to have in place a project manager with basic knowledge of the customer's system products and who would be capable of unifying management for the project. Within NEC Electronics itself, this project review meeting served as the impetus for the acceleration of the creation of a project framework for transforming the V850 Series into a system LSI CPU core. Moreover, the experience gained in this first project was applied to other projects focused on applications including printers, mobile phones and digital cameras. This led to the development of V850E1 core and V850E2 core, both of which are common with ASICs. There was also a connection between the creation of this IP core and improvement in the development speed (reduction of development TAT) of microcontrollers themselves, and this resulted in the accelerated development of multipurpose products.
In December 2003, the shipping volume of products equipped with 32-bit V850 microcontroller cores reached the 300 million mark. Nearly 11 years had passed since the start of development in 1992. Over that period of time, numerous people had participated in a wide variety of related projects for which there were many memorable episodes and dramas filled with human emotion. Through all that happened, the engineers involved showed that no matter what difficulties you find yourself faced with, you must never give up. Although it is unknown what new stories will unfold in the future, it is certain that the story of the challenges and passion behind the V850 Series will continue.
