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Presented at X-Day 2011, Israel: Many systems produced 10 or 20 years ago are still viable, but finding parts to replace their old processors is often impossible. An excellent solution is to use legacy IP cores -- such as for a 68000 -- implemented in modern Xilinx FPGAs. Moreover, the great capacity, high speed, and low power consumption of Xilinx devices can provide easy opportunities for significantly improving the competitiveness of existing products.
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November 6, 20111
Cost-Effective System Continuation using Xilinx
FPGAs and Legacy Processor IP
Nikos ZervasVP Marketing, CAST, Inc.
November 6, 2011
Why System Continuation?
2
Many 10 – 20 year old systems are still viable …
… but finding parts to replace their old processors is often impossible.
November 6, 20113
Why System Continuation?
• One good solution in some cases:– Use legacy IP cores, e.g., 68000.– Implemented in a Xilinx FPGA.
• Modern FPGA features also provide opportunities for further system improvement.
November 6, 20114
Extending EoL’d Systems
• How to extend the life of products using processor chips past their End of Life?1. Replace with a currently-available chip, rewriting
software as necessary.2. Emulate old processor using extra cycles
available with a new processor.3. Develop your own plug-in, instruction set
compatible replacement with IP on an FPGA.
• Some significant challenges with #1 …
November 6, 20115
1. Chip Replacement Challenges
• Making modern chip work with old software.
The customer initially might have considered replacing the original 68HC11 hardware with a completely different processor, but this approach would have required replacing the application software. That would have been a daunting task, because the software was written in tight relation to 68HC11 instructions and internal peripherals. Consequently, switching to a new processor would have required considerable effort and time just for the software redesign.
Using FPGAs to avoid microprocessor obsolescence,John Swan and Tomek Krzyzak, EE Times, 3/5/2008
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1. Chip Replacement Challenges
• Re-satisfying Food and Drug Administration or similar regulatory certification requirements.The original customer for this design makes air data computers, and projects demand to continue well beyond when the "obsolete part stock" quantities of the Z8000 will be around. Since the software for this system has to be FAA certified, changing even one line of code is horrendously expensive.
Monte Dalrymplr, EDAboard discussion http://www.edaboard.co.uk/obsolete-processors- resurected-in-fpgas-t414369.html
November 6, 20117
2. Replacement via Emulation
• Take advantage of the extra capacity of a modern processor to run an emulation of the legacy device.
• Reuses existing application software—good—but introduces new code and timing challenges—bad.
• Effort to resolve these challenges can be significant, eroding profit to be gained by system life extension.
November 6, 20118
3. Exact Replacement Can Work
• We’ve found that exact replacement using IP on an FPGA is the best solution for many customers.
• HAPA AG used 68000 IP/FPGA tocontinue life of 15-year-old stepper motor control system in pharma-ceutical printers. Physical space saving enabled new platform improvements.
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Exact Replacement Examples
• Sunplus Technology extended market life of early Sega game consoles replacing obsolete 68000 chip with IP/FPGA.
• A Japanese system manufacturer intends to keep critical 68000-based traffic operation control systems functioning several more years by replacing end-of-life’d chips with FPGAs implementing the C68000.
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Exact Replacement Examples
• ThyssenKrupp Elevator used the C80188EC core and Australia’s Defense Science & Technology used the 80186EB core to retain the advantages of still running Windows 3.1 for Intel® 80C188EC processor chips.
• Fabless provider Innovasic Semiconductor cost-effectively developed new niche markets for 8051 and 80186 discrete chips using CAST controller cores
November 6, 201111
Replacement Approach Factors
• End User Product Life — Longer life increases chance your new processor chip will also become obsolete, so using IP makes sense.
• Software Code Language and Volume — How much assembler code must be rewritten to run with a new processor chip? If software is small and mostly in C, rewriting it for a new processor chip may be easier than using processor IP.
• Licensee’s IC Units per Year — If unit volume is 10 or fewer each year, then future revenue is unlikely to justify the expense of redesigning with a new processor.
• Number of Peripheral Circuits — Peripherals may also be nearing (or past) the end of their availability. If so and if many, then starting with a new processor and its modern peripherals makes sense.
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Replacement Approach Factors
• End-User Equipment Cost — Future revenue rarely justifies the costs of switching to new processor for inexpensive products, unless expected annual unit volume is very high.
• Processor-Specific Chip and Programming Experience — If the original programmers of the legacy processor are no longer available, then continuing maintenance will be difficult, possibly moreso than switching to a newer processor.
• Experience using IP and FPGAs — If design team has little such experience, then using a discrete processor chip is likely the better approach.
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Case Study: 68000 Replacement IP
• CISC processors• Began 1979 with
Motorola MC68000• 32-bit internal and
16-bit internal• Later second-sourced
by others• Dominant in its day:
Sun & Apollo workstations; Amiga & Apple PCs; LaserWriters
• CAST core introduced 2000, works identically, includes peripheral interfaces, adds JTAG
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Planning A Replacement Project• Two steps:
1. Verify that the IP core is really software compatible.
2. Merge other functions from the board into the FPGA if possible.
• For example, consider this system
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Planning A Replacement Project
• Conceptually, the IP core just replaces the discrete chip
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Planning A Replacement Project
• In practice, also need to:– Burn ROM
image intoFPGA, and
– Control RAM through FPGA
• System I/Os should be initialized by bootstrap code in ROM
• System should start functioning normally, verifying correct operation in the IP core
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Planning A Replacement Project
• Next step: integrate additional functions to take advantage of any extra capacity in FPGA.
• For example, I/O 1 and I/O 2 might fit.
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Other Opportunities
• Many legacy IP core netlists available, e.g.– 8051 and 80251 – 8254 Timer/Counter– 6502 & 65C03 – UARTs– 80186 & variations – 8237 & 82380 DMA
Cont.– 80188EC – 32025 DSP– 68000 16- & 32-bit versions
• Or buy IP core in RTL and modify yourself (or contract with IP vendor)
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Conclusions
• Extending product lifetime past EoL of processor chips can pay off.
• Using an IP core in a Xilinx FPGA is the easiest, cost cost-effective approach for some situations.
• Vendors like CAST have a variety of proven, legacy processor IP available.
• We can help you choose the best approach and best IP for your particular project.
