V305-EB11 DynamicSignals 24-Channel Isolated Digital Input VXIbus

The V305 is a single-width, C-size, register-based, VXIbus module that provides 24 individually isolated, contact sense circuits and a global change-of-state indication. Each sense circuit detects the presence or absence of voltage at its terminals and is suitable for sensing such remote process contact closures as limit switches, machine tool relay contacts, pressure switches, manual switches, and mercury-wetted contacts. Five voltage options are available (TTL, 12 V dc, 24 V dc, 48 V dc, and 120 V ac) as well as a contact input option.

Input isolation is achieved by using LED/photo-transistor optical isolators. Each circuit (except the TTL version) is a floating, two-wire circuit with common-mode voltage isolation greater than 500 V. Each option has 24 circuits with identical input voltage ratings, and the switching threshold is approximately one half of the rated input voltage. Each input circuit draws more than 5 mA but less than 10 mA. The logic convention is such that a contact closure (input voltage present) is interpreted as a logical” 1.” Each input is conditioned by filtering after the optical isolator. The filter time constant is 100 ms. Other time constants are available by special order.

The V305 contains a 24-bit memory register and a 24-bit comparator. If one or more of the inputs has changed state (1-to-0 or 0-to-1) since the last time the memory register was updated, a common interrupt source is set. This can produce an Interrupt Request directing the computer to read the current state of the inputs.

The V305 supports both static and dynamic configuration. Access to the data is through memory locations indicated by the Offset Register within the VXIbus Configuration Register set, using A24/A16, D16 data transfers.