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.

1. Cost-Effective System
Continuation using Xilinx
FPGAs and Legacy Processor IP
Nikos Zervas
VP Marketing, CAST, Inc.
1 November 6, 2011

2. Why System Continuation?
Many 10 – 20 year old
systems are still viable …
… but finding parts to
replace their old
processors is often
impossible.
2 November 6, 2011

3. 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.
3 November 6, 2011

4. 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 …
4 November 6, 2011

5. 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
5 November 6, 2011

6. 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
6 November 6, 2011

7. 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.
7 November 6, 2011

8. 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 to
continue life of 15-year-old stepper
motor control system in pharma-
ceutical printers. Physical space
saving enabled new platform
improvements.
8 November 6, 2011

9. 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.
9 November 6, 2011

10. 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
10 November 6, 2011

11. 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.
11 November 6, 2011

12. 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.
12 November 6, 2011

13. 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
13 November 6, 2011

14. 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
14 November 6, 2011

15. Planning A Replacement Project
• Conceptually,
the IP core
just replaces
the discrete
chip
15 November 6, 2011

16. Planning A Replacement Project
• In practice,
also need to:
– Burn ROM
image into
FPGA, 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
16 November 6, 2011

17. 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.
17 November 6, 2011

18. 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)
18 November 6, 2011

19. 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.
19 November 6, 2011