Index pulse for encoder on MOT module

dmgleichman · Joined: 28 Oct 2008 Posts: 2 Location: Torrance, CA

We have a SBC6713e with a MOT module and a SERVO16 module and we have been using several of these setups for a couple years now for our motion control systems. We have used the quadrature decoders on the MOT module before, but now, for the first time, we are using the index pulse besides the A and B outputs, and we can't get it to work. We have seen in the manual that you have to have the home input low also before the index will pass through to the LS7266 decoder chip. We did that but it still doesn't work. Can you provide more details as to the circuitry that lives between the input to the board and LS7266 LCTNR/LOL pin? We would like it to go directly in, but you seem to have some latch circuits that gate the signal. How do you make it work with just a plain encoder with A, B and I outputs? Thanks.

jhenderson · Posted: Wed Nov 03, 2010 2:18 pm Post subject:

From the OmnibusHardwareMaster.pdf manual, pg 165:

The home and index inputs are single-ended TTL and falling edge sensitive. Are you sure that you're generating a clean falling-edge on both home followed by a falling edge on index? I think this is necessary for the 7266 to see the pulse.

dmgleichman · Joined: 28 Oct 2008 Posts: 2 Location: Torrance, CA

What is the timing requirements for these two edges? Can they happen at the same time. Or on the otherhand, is there a maximum time that one has to follow the other by?

jherring · Joined: 12 Apr 2006 Posts: 52

Logic on the MOT module qualifies the differential index signals from JP29 on the home signal (home and index both low to generate an active low output to the LS7266 XLCNTR* input). The external index signals (connector JP31) are OR'd into the output signal and thus are not qualified and pass directly through to the XLCNTR inputs (i.e. if the external index signal goes low, the XLCNTR input will go low).

The differential index signals are received from the JP29 I/O connector via RS422 receiver devices, and then piped to the board logic. The index signals may be driven either single-ended or differentially, but if single-ended use is required then the signal must be connected to the positive index input. All signals are 5V logic/RS422 levels at the connectors.