Update on this: I did put together a battery and voltage divider to
test the AXV11. The label on the A/D module says it brings the output
from the multiplexer to one of the external pins. I was able to verify
that the voltage applied to a couple of the A/D inputs makes it through
the multiplexer when selected using the CSR. The next output available
is from the Sample and Hold, and this is always pegged at +12v. Am I
wrong to assume that the sample and hold will 'freeze' its output when
the A/D go bit is set?
At least the D/A's work on the AXV11 I have! Glass half full.
Next tried the Data Translation DT2762 with the voltage divider source
and this board appears to work correctly. What I was able to observe
was by applying different voltages to the input I see different binary
values in the DBR.
The manual from bitsavers for this board lists a complete Macro
diagnostic program in an appendix. Does anyone have an electronic copy
of this Macro code? Or the compiled utility?
Doug
On 2/6/2022 1:55 PM, Jerry Weiss via cctalk wrote:
These A/D systems use methods to isolate the sensitive analog signals
from the electrical noise and ground plane of the computer. Typically
a differential input is standard, so you will probably need wire up
two inputs.
If this is your first time with A/D, suggest you toggle in some code
to trigger and report the A/D conversion repeatedly and use a small
voltage battery with a potentiometer divider to drive the inputs.
Most of the analog inputs should be high impedance and while not
impervious, can take +- 30v w/o damage.
Jerry
On 2/6/22 11:43 AM, Douglas Taylor via cctalk wrote:
Yes, I am putting 1 into the CSR to start the conversion and I do get
a 200(8) indicating that the conversion is complete. I wonder if
this means the A/D chip is OK but something else, like the
multiplexer chip or gain amp is fried.
On 2/6/2022 12:33 PM, Jerry Weiss via cctalk wrote:
Are you triggering an A/D conversion via the CSR or external
signal? Then check the A/D done bit.
See EK-AXV11-UG-02 Chapter 4.
Jerry
On 2/6/22 11:20 AM, Douglas Taylor via cctalk wrote:
I have one of these and would like to use it, however it appears to
only partially work. Here is what I have found that works and what
doesn't:
1. CSR and DBR are present and operational.
2. Jumpers set to 'factory'.
3. D/A portion works, can deposit codes in ODT and see voltages out
on DAC pins that change depending on the octal value deposited in
CSR+4 or +6.
4. A/D portion returns full scale code, either 3777 (2's
compliment) or 7777 (offset binary) whether in the input is open or
shorted to gnd.
I think the problem is that the A/D inputs are not exactly
protected and damage has occurred to this portion in the past.
Does anyone have any info on the A/D module? Who made it? Can you
open it up? Does XXDP have a test for this?
Doug
