HP Integral PC Manuals

Tony Duell ard at p850ug1.demon.co.uk
Mon May 5 12:58:37 CDT 2008

> Checked today, and the floppymotor keeps on running...

And you have V1.0 ROMs, yes?

I think we can assume there's not a hardware fualt on all 3 machines (my 
2 and yours), and that the floppy was designed to keep running. I wonder 
why? The MotorOn line is certainly software-controlled, it's not simply 
tied low or anything.

> Pictures are made and on it's way to you.

Thanks, I've seen them. The ROM module is very different to my V5.0 one. 

2 ohter errors I've spotted in 'my' Integral schematics :-(. 

1) Input 0 of the Interrupt priority encoder should be tied to ground, 
not +5V. In fact this would make no differece to the operation of the 
machine (the only ontput to change state isn't used!).

2) The commonned pins on the floppy drive connector on the logic B PCB 
are not suprisingig also grounded. I must have just missed off the ground 
symol :-)

Anyother thing that might be of interest is that there's a 10Hz 
'heartbeat' on the IR1 interrupt line, it comes from the real time clock 


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