What is 1451?
IEEE 1451 Working Groups
301 975 6602 Telephone
301 990 3851 Facsimile
100 Bureau Drive,
Gaithersburg, MD 20899-8220
What is an NCAP?
A Network Capable Application Processor (NCAP) is a device between the STIM and the network that performs network communications, STIM communications, data conversion functions, and application functions. It also provides power to the STIM circuitry. The NCAP usually contains a controller and the interface to the broader network that may support other nodes. An NCAP could be an 8-bit microprocessor for a DeviceNet control network, or a 32-bit microprocessor for an Ethernet-based control network. Once a TEDS is read, the NCAP knows how fast it can communicate with a STIM, how many channels a STIM contains, and the data format of each STIM's transducer. It also knows what physical units are being measured, and how to convert the raw readings into corrected SI units.
A STIM driver is comprised of 4 major functions:
- Software interface driver: responsible for getting data across the interface
- TEDS parser: has knowledge about the 1451.2 TEDS structure and assembles the data into meaningful pieces
- Correction engine: the algorithm that converts raw readings from the STIM into units specified in the TEDS for sensors or units specified in the TEDS into STIM settings for actuators.
- 1451.2 Application Programming Interface (API) driver: provides access to TEDS blocks, sensor readings, actuator control, triggers and interrupt requests.
How can an NCAP be used?
An NCAP initiates a measurement or action by means of triggering a STIM, and the STIM responds with an acknowledgement once the function is completed. The STIM can interrupt the NCAP if an exception such as hardware error, calibration failure, or self-test failure has occurred.
What can an NCAP be used for?
An NCAP can be used as a node controller in a multiple-node network. It can communicate with other NCAP nodes via the client/server protocol or publish/subscribe protocol.