By allowing multiple applications to reside on the same smart card, the MULTOS operating system has the potential to provide cardholders with a single card that they can use to access a variety of different services, such as banking, pay-TV, mobile phones and travel ticketing. Capable of downloading, validating and locking each application into a firewalled area of the smart card’s memory, MULTOS will enable individual smart-cards to be customized on-line to suit their owner’s lifestyle. And by allowing the cost of the cards to be shared by a number of different service providers it will significantly reduce the cost of implementing the next generation of smart card systems.

"Because the MULTOS smart card virtual machine is stack-based and has to run with very limited memory resources, every single application instruction generated by the compiler really has to be justified. We do not believe there is any other compiler development platform we could have used that would have achieved such good results in a similar amount of time." Matt Newsome, Senior Engineer and Project Leader for Compiler Development at Hitachi Micro Systems Europe

However, the necessity for multiple applications to reside on the same card, and for these applications to be securely partitioned from one another, means that MULTOS application programs must be as code efficient as possible if they are to fit into the limited memory capacity of smart cards. To assist in code density, MULTOS-based applications are normally written in, or compiled to, MULTOS Executable Language (MEL) a smart-card optimized language that runs interpretively on a virtual machine implemented by the smart card’s microcontroller.

Hitachi’s C compilers for MULTOS applications that run on the company’s H8 range of 8-bit smart card microcontrollers compile C programs into an intermediate language called MAL (MULTOS Application Language), which is then passed through the company’s MALT assembler/linker tool to generate MEL byte code that can be downloaded onto the smart card. Critical requirements for Hitachi were not only that the resultant MEL code was as compact as possible, but also that the application program as a whole minimized stack usage. With some devices having as few as 70 bytes of on-chip RAM available for the software stack, stack usage could easily become the limiting factor in how complex an application can be.

"Because the MULTOS smart card virtual machine is stack-based and has to run with very limited memory resources, every single application instruction generated by the compiler really has to be justified," said Matt Newsome, Senior Engineer and Project Leader for Compiler Development at Hitachi Micro Systems Europe. "Fortunately with CoSy, we found that the majority of the global optimizers and infrastructure we needed to produce code-efficient compilers were already built in to the development environment."

The other reason why Hitachi chose CoSy was the level of support provided by ACE. Although it had gained a good deal of compiler experience while working with third party compiler developers, Hitachi Micro Systems Europe had never generated its own compilers for such memory critical or stack critical applications. Bringing compiler development in-house without jeopardizing time-to-market requirements therefore demanded considerable confidence in the development system.

"Having so much of ACE’s IP available in CoSy right from the outset, such as a C front-end and a set of global optimizers, was an enormous advantage when it came to producing compilers within the allotted time scales," said Newsome. "We do not believe that there is any other compiler development platform we could have used that would have achieved such good results in a similar amount of time," he added.

Bringing compiler development in-house has also brought other benefits for Hitachi Micro Systems Europe. Compared to paying a third-party compiler developer it has cut development costs by as much as 60%, with the added ability to leverage IP-reuse in order to reduce the cost and shorten the development times of future compilers. The compilers it has already generated are now an important part of Hitachi’s total smart card offering, which also includes development tools such as an IDE, graphical debugger, and terminal simulator as well as the assembler/linker.

With the assistance of ACE’s CoSy Compiler Development Platform, Hitachi continues to play a leading role alongside companies such as Dai Nippon Printing, Mondex International and MasterCard in helping to support MULTOS in its progress towards becoming the de-facto industry standard for smart card applications.