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Can DMM/Switch Handshaking be done through the PXI Backplane when Using the SCXI-1127/1128?

Hardware: Modular Instruments>>Digital Multimeters (DMM)>>PXI-4070, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4071, Modular Instruments>>Digital Multimeters (DMM)>>PXI-4072, SCXI>>Modules>>SCXI-1127, SCXI>>Modules>>SCXI-1128

Problem: I have a PXI combo chassis in which I would like to perform handshaking between my PXI-407x and the SCXI-1127/1128. Can I route the handshaking lines through the PXI backplane so that no external trigger lines need to be run? If so what trigger lines should I select in the niSwitch DMM Switch Handshaking.vi example for the switch trigger input, scan advanced output and the DMM measurement complete destination, trigger source?

Solution: The SCXI-1127/1128 can send and receive triggers through the backplane of the PXI/SCXI combo chassis in the following manner:
  • Trigger Input: Hardware source: SCXI trigger line 0; Software name: TTL0
  • Scan Advanced Output: Hardware destination: SCXI trigger line 2; Software name: TTL2

Hence, the SCXI-1127/1128 cannot route the Scan Advanced Output to the SCXI Trigger Line 1 (software name TTL1)

The PXI-407x when installed in the right most slot of a PXI/SCXI combo chassis, can control the chassis and exchange trigger signals through the backplane in the following manner:
  • Measurement Complete: Hardware destination: Local Bus Right Line 0, which is connected to the SCXI Trigger Line 0; Software name: LBR TRIG 0
  • Trigger Input: Hardware Source: Local Bus Right Line 1, which is connected to the SCXI Trigger Line 1; Software name: LBR TRIG 1

Therefore, the SCXI-1127/1128 and the PXI-407x cannot handshake through the backplane of a PXI/SCXI combo chassis. They can only perform in synchronous configuration.

If you want to configure the PXI-407x and the SCXI-1127/1128 in handshake mode, then you need to exchange the triggers using the external connections. You will need an AUX TRIG cable to connect the Measurement Complete pin to the Ext Trigger pin on the screw terminal if the SCXI terminal block, and the Ext Trigger pin to the Scan Advanced Output pin on the screw terminal of the SCXI terminal block.

Knowing the pin out of the AUX I/O connector, you can use a SH9MD-AUX cable instead and cut it in half. Pins 6 & 9 correspond to the Measurement Complete and External Trigger In lines respectively. In your program, configure the Switch and the DMM to send and receive triggers externally.

Related Links: KnowledgeBase 30J9TOZO: What are the scanning options for the SCXI-1127/1128 Switch Module?

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Report Date: 04/28/2005
Last Updated: 08/03/2005
Document ID: 3KR8ONPC

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