HP-71 Diagnostics

[KimH]

So it rained again... yesterday

I got a response, no good answer as to why parts of the debugger is built in, maybe this was for the HW-designers to have the functions handy in a module, rather than loading something.

I did try to cut the HALT/OD trace in port 4 which the module uses for the "Take Over" function, as expected the machine did NOT like that. The OS ROM and the Diagnostics ROM are working (read fighting) on the same addresses, which is not good for the HW

Port obviously still works for all other modules.

I copied this text from the HW-IDS - 2.2.2 Hard Configuration

A hard configured device powers-up configured to a specific address. It will not respond to an ID, CONFIGURE , or UNCONFIGUREcommand and a bus RESET will not affect its configuration. If the device has a DAISYOU , it is always driven to the same logic level as its DAISYIN.

What i DID learn is that the 1LK7 CPU can be clocked at 1MHz if the LC circuit gets the right values. I have heard that the 1LK7 was in devices after 2623A..

That's next!

(06-06-2020 04:07 PM)KimH Wrote:  Thanks Dave

I have contacted the seller as i left feedback, no response yet...

Based on your suggestion I looked at the FRAM Chapter 9.. maybe there will be some inspiration, but it does look like the "Module" has to be in PORT 1...

I was almost sure that it was the OD short on pin 11, which took care of that little detail. That pin is marked HALT in all other ports, including the IL one

I have an "exploded" 71 for experiments (and to Control the World) which I could use to "cut" that OD track on the PCB for one of the ports and determine if:

1) the 71 will turn on at all - i honestly suspect it wont, there will likely not be any D-In to configure where the ROM would reside in the memory stack

2) if it does, then poke around (and share what I find here)

In the BRILLIANT 71B Compendium from Sylvain there is a link to a ROM-dump made by J-F, so one is available. Playing with that will have to wait to next time it rains

The journey continues

(06-06-2020 01:28 PM)Dave Frederickson Wrote:  One feature of the Diag ROM and Port 1 is that they be capable of disabling the system ROM. They do this by shorting the Output Disable signal, OD, to VDD.

This is all discussed in detail in the FRAM71 Manual Chapter 11, Using the SYSRAM feature.

The Diag ROM module has the OD pin shorted to VDD and when plugged into Port 1 it disables the system ROM and allows the Diag ROM to take-over.

If you have any further questions regarding the Diag ROM I suggest you contact the seller as he was on the development team for the 71B and probably knows a thing or two more than we do.

Dave