Stepping motor/SGM fast axis

For other scans (stepper, SGM, etc.), we will feed an outside timing signal into into REQ (pin 2) of the NI-PCI-6534. This timing signal will generate a data update and a confirming signal out of ACK (pin 3). The configuration in this case is done by a call of DIG_Grp_Mode() with the following parameters:

HandshakeProtocol = 0 (held ACK protocol)

Edge = 0 (ignored with held ACK)

ReqPolarity = 1 (REQ handshake on falling edge -- but it depends on what we will set the outside signal to)

AckPolarity = 1 (high at data flip, low means data stable)

Delaytime = 1 (prolongs ACK pulse by 200 nsec, 100 nsec before data flip and 100 nsec after; may not be necessary).

At each REQ low, the NI-PCI-6534 will react with a data update after about 250 nsec and signal the data flip with a 250 nsec wide high pulse on ACK during the flip. Active low on ACK means the data is stable. This time the signal out of ACK will be given onto ICLK (pin 46) of the DeltaTau and again a falling edge will signal the new positions are ready. However all other devices (detectors etc.) will be triggerd by the falling edge of the signal, that goes into REQ, because it is closer to the actual motor positions. There is of course a time difference of about 400 nsec between these two signals, but with dwell times in the order or msecs we will put up with this.

Figure 7.1: timing of the handshaking for internal and external timing of the NI-PCI-6534