EDGE RENESAS
 
2005.10/vol.11
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Nikon, a top force in photography, continues to produce its "F Series", the world's leading single-lens reflex cameras. Renesas flash microcomputers are used as controllers in a number of models, including the company's latest F6 flagship film-based model, D50 digital single-lens reflex camera, and D2x high-end digital flagship model. Nikon has selected our devices for many reasons. Among them are the chips' wide range of built-in peripheral functions (timers, A/D converters, etc.) and the timely availability of the system development environment. Also, the low power consumption of our microcomputers helps give the Nikon cameras longer operating times.

 

Nikon Corporation
Headquarters: Fuji Building, 3-2-3 Marunouchi, Chiyoda-ku, Tokyo
Web site URL: http://www.nikon.co.jp/

 

Koichiro Kawamura
General Manager
No. 1 Design Department
Development Division
Imaging Company
Nikon Corporation

 

Riichi Higaki
Deputy Manager
No. 1 Design Section,
No. 1 Design Department
Development Division
Imaging Company
Nikon Corporation

 

Edge: Microcomputers are an essential component in cameras, whether they are film cameras or digital cameras.

Kawamura: Nikon's latest flagship single-lens reflex film camera model, the F6, uses two microcomputers (MCU), as figure 1 shows, and our D2x flagship digital camera model has exactly the same control electronics. Our latest single-lens reflex digital camera model, the D50, two microcomputers, as well, per figure 2.

Higaki: The F6 film camera uses Renesas H8S/2643 and M16C/62P devices. The H8S handles operations such as auto-focus, mirror up/down, aperture, and film winding. The M16C performs control functions such as light sensing and the LCD display.

On the D50 model, an H8S/2633R is used as the main MCU. It handles most of the camera's functions. Another Renesas chip is used as the sub-MCU.

The F6 incorporates the type of functions you would expect on a flagship model. The auto-focus function uses eleven distance measurement points, while the light sensing function uses an RGB sensor with 1005 gradations. However, because the camera is capable of taking photographs continuously at a speed of up to eight frames per second, two microcomputers are needed to provide adequate performance because the auto-focus and light sensing functions are performed independently for each frame during this continuous operation.

The D50 digital camera, on the other hand, uses five distance measurement points for auto-focus and has an RGB sensor with 420 gradations for light sensing. These characteristics, coupled with a maximum picture-taking rate of 2.5 frames/second, means that a single H8S is adequate to handle all of the different processing tasks.

 

Nikon's flagship single-lens reflex film camera model, the F6

Latest single-lens reflex digital camera, the D50

Flagship single-lens reflex digital camera, the model D2x

 
Flash microcomputers let Nikon install software upgrades without making major model changes
 

Edge: High-performance microcomputer processing seems to be essential for your cameras. What expectations do you have for flash microcomputers?

Higaki: If a camera control system is based on a microcomputer that uses external memory, then obviously a bus is required to connect the memory, and the resulting increase in pin count means a bigger MCU package. Cameras have a very large number of sensors, operating buttons, and other connections, and the MCU that controls these items requires a large number of pins, so using up available pins for a memory bus seems very wasteful. For this reason, we had been using single-chip microcomputers even before we adopted flash microcomputers.

We started using flash microcomputers around 1995. A major reason for this was the expectation that this would reduce the turn-around time (TAT). However, our use of these devices was limited to the camera development phase and, until recently, we used mask ROM chips in all production models.

Kawamura: From the F6 camera, however, we have started using flash microcomputers in production models also. A key reason for doing this is that software can be modified without involving a major model change.

Models with a single digit after the "F", such as the F6, represent Nikon's flagship models of single-lens reflex film cameras. These are these long-lived products, with a life cycle of about ten years. However, new algorithms for light sensing or auto-focus are likely to be developed during the ten-year time between model changes. For this reason, we have to be able to provide incremental upgrades after the camera has been sold to meet the evolving needs of professional cameramen. The use of flash microcomputers from the F6 onwards means that software upgrading is now possible, and that capability allows us to meet a wide range of different and changing requirements.

On the other hand, we have used flash microcomputers in the production models of our digital single-lens reflex cameras since the D1 series went on sale in 1999. Digital cameras were seen at that earliest stage of the market, in a good sense, as being "cameras that are progressively upgraded," so our adoption of flash microcomputers to meet this need was an inevitable consequence.

 
Timely availability of a development environment is essential for applying new microcomputers
 

Edge: What is your impression of Renesas flash microcomputers?

Higaki: It is not just the fact that they are flash microcomputers, but also their suitability for use as a controller. When we first looked at flash microcomputers, we were impressed by the wide range of timer-related functions and by their ease of use. Because the microcomputers are to be used as controllers, the range and performance of the internal peripheral functions are just as important as the performance of the processor core. Renesas microcomputers incorporate many different peripheral functions such as A/D converters and advanced timer functions, and those features help make the devices easy to use.

Kawamura: We were also impressed by the high degree of code efficiency the Renesas chips achieve and by their ability to keep power consumption low while providing high performance. The latter is a big advantage in battery-operated systems such as cameras. Although digital cameras appear to use a lot of power in the image processing engine or when writing to a flash card, these functions are only used immediately after taking the picture, so they don't involve long processing times. By contrast, the controller unit consumes power continuously while the camera is waiting with the shutter half-pressed. In fact, it is the controller unit that places the largest drain on the battery. The length of time spent with the shutter half-pressed to avoid missing the opportunity for a shot is longer than you would expect, so the lower the power consumption of the microcomputer used as the controller, the better.

Edge: How do you find the system development environment?

Higaki: The range of excellent tools provided by the Renesas development environment is another important point. In particular, the debugger for the M16C is well regarded by developers.

Kawamura: The fact that Renesas makes the associated development environment available promptly when samples of new microcomputers are released was a large factor in our decision to use your microcomputers. Somehow, the availability of development tools for the latest microcomputers from some suppliers always seems to be delayed. But if the development environment is not ready, how can we start development or even evaluate the new devices? Renesas, though, provides the latest microcomputers on a just-in-time basis for our development schedule, and easy-to-use tools always accompany the new chips. This is a big help to us. We have high expectations for Renesas, not just as a vendor of flash microcomputers, but also as a development partner.

Edge: Thank you both for speaking with us today.

 

Figure 1: The F6 SLR film camera uses an H8S/2643 microcomputer and an M16C/62P device.

 

Figure 2: The main MCU in the Nikon D50 digital SLR camera, a Renesas H8S/2633R flash microcomputer, handles most of the camera's functions

 
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