i1990A SPECIAL FEATURES Upgrade of DS1990 allows multiple Serial Number iButtons to reside on a common bus Unique 48鈥揵it serial number Low-cost electronic key for access control 8-bit CRC for checking data integrity Can be read in less than 5 ms Operating temperature range of -40掳C to +85掳C COMMON iButton FEATURES Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48- bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike. Multidrop controller for MicroLAN. Digital identification by momentary contact. Chip-based data carrier compactly stores information. Data can be accessed while affixed to an object. Economically communicates to bus master with a single digital signal at 16.3k bits per second. Standard 16 mm diameter and 1-Wire protocol ensure compatibility with iButton family. Button shape is self-aligning with cupshaped probes. Durable stainless steel case engraved with registration number withstands harsh environments. Easily affixed with self-stick adhesive backing, latched by its flange, or locked with a ring pressed onto its rim. Presence detector acknowledges when reader first applies voltage.