Specification and Design of Quasi- Delay-Insensitive Java Card Microprocessor Fu-Chiung Cheng & Chuin-Ren Wang Dept. of Computer Science and Engineering Tatung University Taipei 104, Taiwan R.O.C.

Outline 1. Motivation 2. Smart Card Architecture 3. Introduction of Java Card 4. Java Card Processor Organization 5. Specification : Data Dependency Graph 6. Implementation and Optimizations 7. Conclusion

1. Motivation ID card, driver license, credit cards, bank Cards, library card, p ay-phone card,... => Smart Card Other applications : [Henry97] –fraud control for credit and debit cards –access control for buildings or computer systems –ticketless travel on airlines, subways, buses or trains. Java Card is a smart card using Java technology.

1. Motivation Why Asynchronous circuit for Java Card Microprocessor? [Hauck95,Cheng97] –low power consumption –average-case performance –robust –Modularity, Composability, Reusability

2. Smart Card Architecture Smart card architecture consists of – CPU – memory – communication interface The front and back of Smart card:

2. Smart Card Architecture Smart Card CPU: –8-bit, single-tasking devices with 1KB of RAM or less. On-Card Memory –ROM (Read-Only Memory) –RAM (Random Access Memory) –EEPROM (Electrically Erasable Programmable Read Only Memory)

2. Smart Card Architecture Communication Interface – A smart card does not contain its own power supply, display, or keyboard. Card Acceptance Device (CAD) – A smart card interacts with a Card Acceptance Device (CAD) through the communication interface

3. Java Card Java Card is a smart card using Java technology. Java programs run on Java Virtual Machine (JVM). JVM is an interpreter to execute bytecodes (Java instructions). JVM is a stack-based machine. Java Card instruction set is a subset of Full Java’s.

3.1 Data type in Java Card Two kinds of types: primitive types and reference types. Primitive types –byte : 8-bit signed two’s-complement integer. –short :16-bit signed two’s-complement integers. –int : 32-bit signed two’s-complement integers. –Boolean : 8-bit, TRUE or FALSE. Reference types –class types, interface types, and array types.

3.2 Java Card Instruction Set Java Card 2.0 has 104 instructions. 1. Load/ Store Instructions: iload, istore, Arithmetic Instructions: iadd, isub, ior, Type Conversion Instructions: i2b, i2s. 4. Control Transfer Instructions: ifnull, if 5. Operand Stack Management: pop, dup, Object Creation and Manipulation: new, getfield 7. Method Invocation and Return Instructions: invokespecial, invokestatic, return, Throwing and Handling Exceptions: athrow.

4. JAVA Card Processor Organization PC: program counter SP: stack pointer IR: instruction register MAR: memory address register MI: memory interface A, B: two general-purposed registers FB: Frame-based register : Control line : Bus line

5. Specification: Data Dependency Graph Given an instruction set + a processor organization, micro-operations of instructions may be specified by data dependency graphs [Nanya94]. The micro-operations can be directly mapped into quasi-delay-insensitive components. Five basic components: fork, join,select, merge and oval (micro-operation).

5.1 DDG: Five Basic Elements

5.2 DDG: Java Card Processor Fetch Instruction Decode Execution

5.3 DDG: iadd instruction

6. Implementation: Goal: four-phase handshaking QDI circuits [Nanya94,Cheng97]. Mapping DDGs to QDI Components TITAC: point-to-point data transfer Our Java Card Processor: shared bus architecture.

6.1 Shared Bus Architecture

6.2 QDI Library

6.3 Deriving Control Path from DDGs

6.3 C-element and Q-element

Control Path: iadd

6.3 Deriving Datapath from DDGs: For each micro-operation, M, and its Q- element with the start (Ms) and finish (Mf) of this micro-operation: –If M read a register R then connect Ms to the read signal of R. –If M write to a register R then connect Ms to the write signal of R and add a demultiplexer to send out the write acknowledge to Mf. –If there are multiple signals connecting to a read/write signal, add an OR gate.

Datapath Control Path

6.4 Optimization: Goal: better performance, less power consumption and/or less logic. Three optimization schemes: –Redundancy Elimination –Parallel Execution –Common Modularity

6.4 Optimization: Example 1

6.4 Optimization: Example 2 Sharing Common modules:

6.4 Optimization: Results Redundancy Elimination –Micro-operations: 12  9 –Cost and power consumption: save one addition and three data transmission operations. Parallel Execution: –Micro-operations: 9  8 Common Modularity: –Cost: save (n-1)*getTwoOperands. (n is number of instructions in Arithmetic).

A new asynchronous Java Card microprocessor architecture is presented. Data dependent graph is used to specify the micro-operations of Java card microprocessor. Three optimization schemes are applied for better performance, less power consumption and/or logic. New Java Card 2.1 (Mar. 1999) spec contains 186 instructions. We are developing CAD tool. 7. Conclusions