NI6503 output initial states

[Masakikun]

Hello,

I have a small problem with a NI6503. For my equipement, I defined 8 outputs and 16 inputs to control some componants. A the starting of my software (C++),

it's defined each line with the following step :

//output for port0

DAQmxCreateTask  "PiLj"

DAQmxCreateDOChan(hTask,"boardname\port0\linej","",DAQmx_Val_ChanPerLine);

DAQmxStartTask(hTask);

//input for port 1 and 2

DAQmxCreateTask  "PiLj"

DAQmxCreateDIChan(hTask,"boradname\port1and2\linej","",DAQmx_Val_ChanPerLine);

DAQmxStartTask(hTask);

At the end of initialization, if set all output to  FALSE with a writeline function (external light if OFF) :

        data[0] = value?0:1;

        DAQmxWriteDigitalLines(hTask,1,1,TIMEOUT_RW,DAQmx_Val_ChanPerLine,data,&numWritten,0);

After that, I can change the status of each line according to the sequencer of program logic command. I have also

a readline function to retrieve input status from componant: all of this operate perfectly!

But, for output line, the problem is that during intialization step between  DAQmxStartTask and DAQmxWriteDigitalLines light is ON.

In debug mode, I saw clearly, that is  DAQmxStartTask which enable the light and then light is ON (howerver, W1 jumper on board is set to LOW)

When the computer is started no problem, it's only at the software starting: it's observed a kind of light flashing. Even, it's during a short time (<1s),

I'm worry that could trigger my equipement (it's difficult to check that).

This phenomenon appears only after restarting computer and starting software. If I just quit the software and restart it no problem!

How can I do to solve my problem?

Thanks you for your helpfull answering!

Sylvain

[thomas.baudouin · Accepted solution]

Hi Sylvain,

Thank you for posting on this forum.

When the 6503 is configured for output, it outputs a low state for 5ms. Unfortunately, we won't be able to change that because it is the behaviour of the chip.

However, if you select the power up state to low with the switch, you will stay low, and therefore, you won't have a glitch.

If necessary, I suggest that you use an inverter to invert the logic and avoid this glitch.

Best regards,

[Masakikun]

Hi Thomas,

Thank you for your answer! I checked the technical specification of the componant MSM82C55-A. As you explained, this phenomena is due to the behaviour of chip.

Unfortunately, it's too late to implement an inverter (end of project). If equipment controled by my software is powered ON after my software, then this problem of glich

disappears: I will use this solution with a specific starting procedure!

Best regards