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Acc-24M2A Using PFM


RaphaelM
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Hello,

 

I'm trying to drive a stepper motor with encoder on an ACC-24M2A by MACRO ring.

 

I work on a UMAC rack with a Power PMAC CPU and an ACC-5E3 card.

 

The communication by MACRO works. I can see the encoder feedback in the IDE.

 

I have added the jumpers E5 and E6 to generate PFM signal on J11 & J12 connectors (Pinout : Pulse+ 9 / Pulse- 22 / Dir+ 8 / Dir- 21).

 

Motor[9].pDac = Acc5E3[1].MacroOutA[0][2] // PWMC to drive in PFM

 

The Pulse signal seems be wrong. It's a TTL signal but it's to the high level during 95% of the time. It's as if there was an inversion between low and high levels.

 

The PFM_CLK is at 305.72 kHz (M993 = 2298).

 

I have checked the *.PwmDeadTime (MI994) of the acc-24M2A, but it seems be ok (=15, so PFM Pulse width = 49 us).

 

To conclude, the Driver can't detect the edges.

 

Anybody have any idea? I can give more details.

 

Thanks for your help,

 

Raphael

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Are you sure? For now, I have a TTL signal 0 - +5 Volts.

 

There is just something strange concerning the duty rate.

 

If I make an inversion as you say, I will have a negative signal 0 - -5 Volts.

 

Regards,

 

Raphael Millet

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Raphael,

 

The pulse and direction output on most of Delta Tau products are driven by CMOS differential line drivers which meet the standard RS-422 requirements. This means that each line (non-inverting and inverting) are both in CMOS levels. Both inverting and non-inverting signals are always between 0 to 5V. The line driver used on ACC-24M2A in particular has the following thresholds for low and high signals:

 

Vout - High : Min 2.5V

Vout - Low: Max 0.5V

 

The line receiver on the stepper drive combines these complementary signals through a differential line receiver and reconstructs the original pulse and direction signals. Please see the following diagram showing the signal levels compared to the input signal.

 

1651609206_2013-05-1821_22_08-DataSheetsPreview.png.741a669a5282dab3cdcf56347809d03f.png

 

For further information on this line driver, please check the documentation for ST34C87 QUAD RS-422 CMOS Differential Line Driver.

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