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Hi to all
Another annoyance to get my configuration changed to MESA 7i43.

I already used the same HW with normal par port card and I use 5V with active high signalling. I have soldered 1K resistors to ground, parallel to all inputs and switches connecting to +5V when active. This was good enough to get stable signals, also using shielded cable.

Now I'm trying to switch to mesa and by first verifying the input signals with pncconf, the MESA "launch Test" . And I see all inputs flickering randomly from high to low.
If the mesa card was not yet loaded, all inputs stay at 0V, Is I want. After loading the pal program they go up. ( some 1.49 V ) That gives the random reading.
OK, I understood that there is a jumper W3 that can pull all pins to 3.3V. So I took it away. Gave not a better result. Restarted PC same behaviour.
I believe that I understood from the docs that it is possible to set the pull up function additionally by the sw.

My question:
Is it possible the way pncconf works is setting these pull ups always? And where can I change that behaviour?
Means I can keep 1K as normal resistor, as 5mA is enough. I don't want to install a heating just to see some input signals.

Mike

Heres the relevant 7I43 manual page (page 18):

OPERATION
STARTUP I/O STATE
When the 7I43 is used to control external equipment that is sensitive to the initial
pin states, the pre-configuration pull-ups should be enabled (W3 UP), and for most
configurations, pull-ups resistor should be configured on any I/O pin that is not driven when
configuration is complete (bi-directional pins and pins whose function is assigned by
software). Since the only definable pre-configuration state is with pull-up resistors on the
I/O, this means the proper I/O polarity is active low (so that all outputs are in the in-active
state at power up)

All pins default to High at startup. any other option will have problems
so any home built daughtercards should follow this standard.
If they do not you will have to have work-arounds on every pin and lots of trouble

Hi PCW

I know.. On other places in manual you write that pull-up can be switched on and of by SW.

I'm talking only of input-mode.

1K is not enough to get low signal.

There is an resting "offset" of 1.49 V. Means in my eyes that ca 1.5mA are driven by the board.
So pull up seems to be also in the range of 1K.

I want to use Input with floating pins.

How can I get that by hostmot2 ?

Mike

By removing the pull down resistors and following the high=inactive standard

That is to say the 7I43 (and all of our FPGA cards) are designed for
active low inputs and outputs, for output safety, OPTO22 compatibility and
compatibility with the FPGAs HotSwap/ preconfiguration mode.

This means its much easier to use active low I/O and use the built in pullups

Note that this same situation applies to parallel port inputs, they normally have built in
pullup resistors (the original IBM design has 4.7K pullups to 5V on the input pins)
which means pulldowns (unless they are very stiff) will lead to marginal I/O voltages