• Please review our updated Terms and Rules here

M8189 bootstrap error LED's D1 and D4 on

Looking at the picture of your assembled board posted above, it looks like some of the resistors were not populated correctly (ie, values in locations swapped).
I can't view it in high enough resolution to be 100% sure, but it looks like the highlighted resistors in the below annotation are incorrect (values are incorrect for the position):

Capture.PNG

The net effect is that some data/control lines will be incorrectly terminated and cause signaling errors. Like a data line always stuck high.

AND I just noticed your LEDs are incorrectly stuffed as well. D1 should be RED (is YELLOW), D2 should be YELLOW (is GREEN), D3 should be GREEN (is RED).

I suppose in the source file led_driver.cpp you could just swap around the pin definitions for which pin gets driven for red/yellow/green and fix it there.

But the resistors need to be swapped to be the correct value in the correct positions for the board to operate correctly. No option.
 
Last edited:
I correctly re-populate all resistors per posted schematic but the result is still the same. No booting occurs. In addition, I rotate 180 degrees the 40-pin cable, the data lines are still continuously asserted. Below are the display of RS232 of M8189,
1683292704986.png
I have no idea the functionality of my M8189 and the associated controller boards including my RX02 emulator. Does anyone have experience using M8189 ?
 
Also when electronics have a weird behavior it's often the power supply that is not providing enough power.
 
The DDV11-B is described as an 18-bit backplane.

The KDF11-BA CPU is claimed to be compatible with both 18 and 22 bit backplanes. I can't see any links related to this...

If the backplane is 18-bit, all of the other cards must be 18-bit compliant also.

I assume the DCOK signals etc. are fully functional?

Dave
 
Daver2 and jplr,

Where is the DCOK signal ? I measured the 5 volt and the reading is 4.1V only. 4.1V is too low. How do I confirm with the DCOK ?
 
As you say, 4.1V is too low.

I suppose I should have said BDCOK and BPOK. These are sourced from your power supply and should be wired to the QBUS signals.

Dave
 
These signals are available at the back of the backplane (this is an example for LSI-11).

1683306978194.png
 
Last edited:
Cmao, please could you post a photo of the back of the backplane, especially where there are markings such as "part N° H123456"?
 
It is weird. Both the readings of BPOK and DCOK are 4.6V and the voltage reading on Vcc pin of the ROM chip is 4.1V ???
 
There is very little current flowing in the control signals - so there will be very little voltage drop across the cables. However, 4.6V is still too low!

The main 5V rails will have an appreciable current flow - and hence voltage drop.

Dave
 
>>> You meant there are problems on backplane sockets?

Unlikely. I would check the cables from the power supply to the backplane...

Dave
 
I tested the voltage drop for each board. I inserted one board at a time to the backplane. Here are the voltage drops:

0. the bare backplane: 5.06V

1. M8189: voltage drop from 5.06V to 4.43V.
2. M8029 (RX02 controller): voltage drop from 5.06V to 4.87V.
3. M8067 (memory board): voltage drop from 5.06V to 4.53V.

Here is the question:

Does DEC boards always drain lots of current? or Isn't AXT power supply good power source for PDP-11 system?
 
You must log in or register to reply here.
Back
Top