11/45 progress

[Tony Duell]

> 
> Ok, found the jumpers for the DL11 in the schematics section on bitsavers. I 
> have two M7800's, one is set for 777560 and one is set for 776500.

OK, a farily standard pair of addresses. The former is the console port.

> 
> I'm assuming that when a card is jumpered so (the high bits are constant 
> anyways), that it appears exactly at that address no matter how much memory 
> is installed in the machine (ie. it doesn't move around based on maxmem).

Absolutely. 

> 
> Anytime I exam 777560 I get an address error. If I exam 776500, I get a 200, 

Odd... That implies your console card is not responding. Maybe it's 
defective too. 


> but anytime I store a value and read it back, there's all zero's in the data 
> register.

You shouldn't be able to read/write all 16 bits -- some of them plain 
don't exist in the heardware, some are read-only. But IIRC there's at 
least one bit (my memory is weak on this, but I think it's the interrupt 
enable bit, maybe bit 6) that you should be able to read and write from 
the panel.

My idea was going to be to hang a terminal off the card (assuming you 
have an RS232 lead and can decode the word foramt and baud rate settings 
[1] and then try writing to the transmit data registers at 777566 or 
777656. See if you can transmit chracters to the terminal.

[1] The baurd rate is set by a rotary switch on the card and by the 
frequency of the crystal fitted. I found the quickest way to work it out 
was to connect a frequncy counter to pin 17 (Rx clock) and 40 (Tx clock) 
of the UART chip. Then divide that frequency by 16 to get the baud rate. 
But I guess you don't have a frequency counter sitting on top of your 
machine...

> 
> Methinks the problem wasn't memory, but something amiss in the cpu section. 

So do I.

> Bummer as I have no spare cpu cards. But I guess at this point I still don't 

I am going to get you to repair that machine properly -- without swapping 
boards -- even if I have to get on the next p'lane across the Pond and 
show you where to stick your 'scope probe ;-)

> know if it's a unibus problem or a cpu problem.
> 
> Something else I noticed is the terminator cards in front and back as well 
> as the cpu backplan to MF11-L had what I would think is a lot of "up down 
> wiggle" in them. I'm quite sure they are seated completely, but I can turn 
> them up or down more than I would think one should be able to. Is that 
> common?

You have got them in the right way round, with the resistors towards the 
front of the machine, I hope! If not, you will have all sorts of 
problems. 

> 
> Hopefully sage listemembers can offer some advice as to where to go next :)

Ge ta Unibus pinout, grabe the logic probe, and see if the data lines 
ever go low on a CPU (frontpanel) write operation.

-tony