Understanding Smart Sensors - Nomads.usp

Standards for Smart Sensing 285• Channel timing read/write setup time, sampling period, warm-uptime, and update time;• Power supply requirements (voltage and current);• Overhead: the TEDS length and number of channels.Eight different TEDS memories are defined in 1451.2. The types ofTEDS are either for use by the NCAP (machine readable) or for operators(human readable). There are two mandatory and four optional TEDS classifications.Table 12.2 lists the types of TEDS that are defined in 1451.2 [5].Figure 12.11 shows the addressable sections of the TEDS [8]. The mandatorysections are shown with solid lines, the optional sections with dottedlines. The standard was defined to provide a growth path for futureapplications.Table 12.3 shows an example of one of the TEDS in 1451.2—the datastructure in the mandatory channel identification data block [6]. The 17 fieldsprovide manufacturer- and sensor-specific information. The function of thechannel identification TEDS is to make available at the interface all the informationto identify the channel being addressed. The channel identificationTEDS bytes are constant and read only [6].12.4.3 TIIThe standard digital interface for IEEE 1451.2, TII, is a clocked serial interfacesimilar to an SPI (see Section 6.9.1). The 10 electrical connections are definedTable 12.2Types of Transducer Electronic Data Sheets (TEDS) [5]Type Readable By IEEE 1451.2 MandateMeta TEDS Machine MandatoryChannel TEDS Machine MandatoryCalibration TEDS Machine OptionalGeneric-extension TEDS Machine OptionalMeta-ID TEDS Human OptionalChannel-ID TEDS Human OptionalCalibration-ID TEDS Human OptionalEnd-user application-specific TEDS Human Optional