DS2415P Analog Devices

DS2415 1-Wire Time Chip www.maxim-ic.com FEATURES PIN ASSIGNMENT Real-time clock with fully compatible 1- Wire MicroLAN interface Uses the same binary time/date representation as the DS2404 but with 1 second resolution 6-Pin TSOC PACKAGE Clock accuracy 2 minutes per month at TOP VIEW 25C Communicates at 16.3kbits per second 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 8-bit family code specifies device communication requirements to bus master PIN DESCRIPTION Built-in multidrop controller ensures compatibility with other MicroLAN products Pin 1 - GND Operates over a wide V voltage range of Pin 2 - 1-Wire DD 2.5V to 5.5V from -40C to +85C Pin 3 - V DD Pin 4 - V Low power, 200nA typically with oscillator BAT Pin 5 - X1 running Compact, low cost 6-pin TSOC surface Pin 6 - X2 mount package ORDERING INFORMATION DS2415P 6-pin TSOC package DS2415P/T&R Tape & Reel of DS2415P DS2415X Chip Scale Pkg., Tape & Reel DESCRIPTION The DS2415 1-Wire time chip offers a simple solution for storing and retrieving vital time information with minimal hardware. The DS2415 contains a unique, lasered ROM and a real-time clock/calendar implemented as a binary counter. Only one pin is required for communication with the device. Utilizing a backup energy source, the data is nonvolatile and allows for stand-alone operation. The DS2415 features can be used to add functions such as calendar, time and date stamp, and logbook to any type of electronic device or embedded application that uses a microcontroller. OVERVIEW The DS2415 has two main data components: 1) 64-bit lasered ROM, and 2) real-time clock counter (Figure 1). The real-time clock utilizes an on-chip oscillator that is connected to an external 32.768kHz crystal. All data is read and written least significant bit first. The real-time clock functions will not be 1 of 14 112701 DS2415 available until the ROM function protocol has been established. This protocol is described in the ROM functions flow chart (Figure 7). The master must first provide one of four ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM. After a ROM function sequence has been successfully executed, the real-time clock functions are accessible and the master may then provide a real time clock function command (Figure 5). DETAILED PIN DESCRIPTION PIN SYMBOL DESCRIPTION 1 GND Ground pin. 21-Wire Data input/output. Open drain. 3V Internal power line. Connect a capacitor DD 4V Power input pin. 2.5V to 5.5V. BAT Crystal pins. Connections for a standard 32.768kHz quartz crystal, EPSON part number C-002RX or C-004R (be sure to request 6pF load capacitance). 5, 6 X1, X2 NOTE: X1 and X2 are very high-impedance nodes. It is recommended that they and the crystal be guard-ringed with ground and that high frequency signals be kept away from the crystal area. See Figure 10 and Application Note 58 for details. BLOCK DIAGRAM Figure 1 64-BIT LASERED ROM Each DS2415 contains a unique ROM code that is 64 bits long. The first 8 bits are a 1-Wire family code. The next 48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. (See Figure 3.) 8 5 4 The 1-Wire CRC of the lasered ROM is generated using the polynomial X + X + X + 1. Additional information about the Dallas Semiconductor 1-Wire Cyclic Redundancy Check is available in the Book of DS19xx iButton Standards . The 64-bit ROM and ROM Function Control section allow the DS2415 to operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section 1-Wire Bus System. 2 of 14