The PICmicro® MCU as an IEEE 1451.2 Compatible
Smart Transducer Interface Module (STIM)
Authors: Richard L. Fischer
Microchip Technology Inc.
This application note discusses the organization of the
PICmicro MCU and related firmware for developing
IEEE 1451.2 Smart Transducer Interface Modules
(STIM). Although a detailed understanding of the
1451.2 is not required, a working knowledge of 1451.2
concepts like Transducer Electronic Data Sheet
(TEDS), STIMs, data models, etc., is assumed. The
purpose of this application note is to provide the devel-
opers of a PICmicro MCU based STIM with some key
hardware and firmware building blocks, that may be uti-
lized in the development of a STIM.
The IEEE 1451 standard is composed of four parts,
1451.1, 1451.2, 1451.3 and 1451.4. The combination
of the four parts (some parts are approved and others
are pending) define the signal chain from the analog
sensor to the digital network (See Figure 1). The main
objectives of the IEEE 1451 standard are to:
• Enable plug and play at the transducer level
(sensor or actuator) by providing a common com-
munication interface for transducers.
• Enable and simplify the creation of networked
• Facilitate the support of multiple networks.
The focus of this application note deals with the 1451.2
part of the standard.
The IEEE 1451.2 standard provides the means to con-
nect sensors and actuators to a digital system, typically
a network, via a Network Capable Application Proces-
sor (NCAP). Figure 2 depicts a general distributed
measurement and control application and Figure 3
depicts the functional boundaries relating to the trans-
ducer interface standard, namely IEEE 1451.2.
In simplest terms, the IEEE-1451.2 standard does the
• Defines a digital interface for connecting trans-
ducers to microprocessors.
• Describes a TEDS, “electronic data sheet”, and its
• Defines an electrical interface, read and write
logic functions to access the TEDS, and a wide
variety of transducers.
This standard does not specify signal conditioning, sig-
nal conversion, or how the TEDS data is used in appli-
http://www.DataSheet4U.net/ There is currently no defined independent digital com-
munication interface between transducers and micro-
processors. Each vendor builds its own interface.
Without an independent, openly defined interface,
transducer interfacing and integration are time con-
suming and duplicated efforts by vendors are econom-
ically unproductive. This interface provides a minimum
implementation subset that allows self-identification
and configuration of sensors and actuators, and also
allows extensibility by vendors to provide growth and
2000 Microchip Technology Inc.
datasheet pdf - http://www.DataSheet4U.net/