[Coco] HP64000 was Re: LIF util for OS-9?

[John Kent]

On 4/11/2011 11:12 AM, Willard Goosey wrote:
> On Fri, Nov 04, 2011 at 12:32:40AM +1100, John Kent wrote:
> Yeah, HP was big into the hotkey system. The emulator system sounds 
> like it would be really helpful in debugging hardware, if it lived up 
> to its hype.

Yes the emulator is quite handy. If you are doing real time embedded 
stuff a trace buffer is very useful.
The HP could capture traces before, after or midpoint for various 
address and data combinations.
There where quite a few emulators such as the MICE & Nohau back in the 
1980s that could do that sort of thing.
We used the Intel blue boxes which had real time trace.
The Motorola MDOS emulators were very deficient in that regard.
FPGAs can use the internal block RAM as trace buffers.
Xilinx came to the party with that with their chipscope.
I've heard that many of the ARM chips have internal trace buffers built in.
Chips like the eZ8 and the Motorola 68HC16 had Background Debug 
Monitors, which were single wire ports for jamming instructions on the 
bus and setting break points and so on. JTAG on the ARM chips were the 
logical next progression from that. They were useful to a point, but if 
you wanted to see what lead up to an error condition, a trace buffer was 
invaluable for seeing where the processor ran off the rails.

I did implement hardware breakpoints on my FPGA 6809 system as well as a 
trace buffer, but I never really tested it or wrote any software to use it.

John.

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