DCT and Xilinx team up over Java processor

By Nick Flaherty
EE Times UK
(08/28/01, 07:06:46 AM EDT)

A UK processor design company has teamed up with FPGA maker Xilinx to run its Java processor on Spartan and Virtex FPGAs.

The Lightfoot core is a stack-based hybrid Java core for embedded applications with an 8bit program bus and 32bit data bus developed by Digital Communication Technologies based in Sunbury on the outskirts of London.

The core has been designed from the ground up for Java, with an 8 element stack and 128 instructions that map directly to Java byte code that can be executed in a single cycle. The 8bit program width gives a very low memory footprint so that all the program memory can be stored on a single FPGA.

The design of the core means that half of its instructions can be customisable in software so that other instruction sets such as C or the Java smartcard system can be used alongside the standard J2ME Java implementation. This is particularly useful for combining C-based protocol stacks with quickly developed Java applications in equipment such as an Internet appliance, says Larry Losen, software team leader at DCT.

The 128 extension instructions map to a software file, the softbyte code file, that is linked in at compilation time, rather than having to change the netlist of the hardware.

The core takes up 1711 CLB slices in a Spartan, Virtex-E or Virtex-II FPGA, which at around 30 000 gates means it occupies just 3% of the larger devices, and it runs at between 30 and 40mips.