How to read code from P87C750?

Obsolete data controller from defunct company uses this Philips ucontroller. Units are failing and customer has the option of either throwing out all his
infrastructure when these units fail and spending $$$$ to replace everything, or burning new controller ICs as units fail.
<http://www.datasheetcatalog.org/datasheet/philips/P87C750EBPN.pdf
It looks like the P87C750 comes with a 16-byte encryption table, optionally used to encrypt the contents of program memory.
The only way, it seems, to know if the memory contents has been encrypted is to read the contents and see if it contains legible code.
Is there another means to know if the memory contents have been encrypted?
Thanks.
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On 12/14/2012 1:22 PM, Gary Walters wrote:

1K of code space is not much.
A logic analyzer and a few hours with a working unit and you will have replacement code ready to go.
How many of these units are we talking about ?
2-3 units a month, 2-3 units a year ??
As the company is now gone, what other type of products are in that market place ?
In this day and age, building a replacement is easier than fooling with encryption.
My $.02
hamilton
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On a sunny day (Fri, 14 Dec 2012 12:22:31 -0800) it happened Gary Walters

It should not be impossibe to crack if encrypted, even with all 7 bytes being not 0xff. The plaintext is asm instructions as machine code, it probably starts predictabe with jump, fast computer. I once wrote a 8052 assembler, this seems like a fun project for somebody who is into that sort of thing.
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wrote:

"The Philips 8XC750 offers the advantages of the 80C51 architecture..."
ADVANTAGES of the 8051 architecture???!!!
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John Larkin Highland Technology, Inc

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I hope that's not the sound of The Segue I hear...
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On 12/14/2012 2:18 PM, Gary Walters wrote:
How can I email you directly ?
hamilton
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notax2day at the popular "Y" service.
Thanks.
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On Fri, 14 Dec 2012 13:15:59 -0800, John Larkin

Well, it sure beat the heck out of the preceding MCS-48 architecture!
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On Fri, 14 Dec 2012 16:44:47 -0500, Spehro Pefhany

What was really the worst uP architecture? That RCA 17xx thing?
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On Fri, 14 Dec 2012 15:49:58 -0800, the renowned John Larkin

The early PICs were about unusable for anything complex (ugly paging and no interrupts) and I wasted a bit of time trying. I never used the RCA thing. Maybe some of the 4-bit ones- they were pretty starved of gates.
Best regards, Spehro Pefhany
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On Fri, 14 Dec 2012 15:49:58 -0800, John Larkin

The 68000. Too boring. ;-)
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On Fri, 14 Dec 2012 19:06:24 -0500, snipped-for-privacy@att.bizzz wrote:

Hey, I love the 68K. Its assembly language is practically a higher-level language. The architecture is beautifully symmetric, sort of a 32-bit PDP-11.
It's big-endian and does a move from source to destination (unlike certain popular, barbaric architectures I could name.)
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Operand order is a function of the assembler, not the architecture. Eg: if I use "gas" I get the order you, and "AT&T" prefer if I use "nasm" I get the order intel prefers. endianness OTOH is dictated by the hardware.
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Tell that to Intel.
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On Fri, 14 Dec 2012 16:41:18 -0800, John Larkin

Precisely. ;-)

Too boring.

Um, name be one thing (in this universe) that moves from its destination to source.
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On Sat, 15 Dec 2012 12:31:33 -0500, snipped-for-privacy@att.bizzz wrote:

Intel!
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On Sat, 15 Dec 2012 11:37:13 -0800, John Larkin

Nonsense. I bet you think all programming languages were invented by Intel, then. The "destination" variable is almost always on the left.
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On 12/14/2012 4:49 PM, John Larkin wrote:

Think it was this one: RCA CDP1802
http://en.wikipedia.org/wiki/RCA_1802
The Galileo spacecraft used multiple 1802 microprocessors.
http://en.wikipedia.org/wiki/Galileo_%28spacecraft%29
The spacecraft was controlled by six RCA 1802 COSMAC microprocessor CPUs: four on the spun side and two on the despun side.
spun/despun ????
hamilton
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wrote:

Part of the spacecraft was spin stabilized, the other not (antennas and cameras hate that).
Spacecraft
"The spacecraft was constructed in three segments, which help focus on these areas: the atmospheric probe; a non-spinning section of the orbiter carrying cameras and other remote sensors; and the spinning main section of the orbiter spacecraft which includes the fields and particles instruments, designed to sense and measure the environment directly as the spacecraft flies through it. The spinning section also carries the main communications antenna, the propulsion module, flight computers and most support systems.
http://www.solarviews.com/eng/galfs.htm
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Ahhh. Good memories. I had a book about how to build a COSMICOS home-brew computer (a PCB with among other electronics a hex-keypad and some 7 segment displays) around a 1802. Never build the thing but I read the book several times just to learn about designing stuff around microprocessors.
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