DS2506 64Kb Add-Only Memory www.maxim-ic.com FEATURES PIN ASSIGNMENT 65536 bits Electrically Programmable Read PR-35 Only Memory (EPROM) communicates with NC NC1 8 the economy of one signal plus ground DALLAS DS2506 NC 2 7 NC Unique, factory-lasered and tested 64-bit registration number (8-bit family code + DATA 3 6 NC 48-bit serial number + 8-bit CRC tester) GND 4 5 NC assures absolute traceability because no two parts are alike 8-PIN SOIC Built-in multidrop controller ensures (208 mil) compatibility with other MicroLAN products EPROM partitioned into 256-bit pages for randomly accessing packetized data records Each memory page can be permanently write- protected to prevent tampering Device is an add only memory where additional data can be programmed into EPROM without disturbing existing data 12 3 Architecture allows software to patch data by superseding an old page in favor of a newly programmed page Bottom View See Mech. Reduces control, address, data, power, and Drawings Section programming signals to a single data pin Directly connects to a single port pin of a ORDERING INFORMATION microprocessor and communicates at up to DS2506 PR35 Package 16.3 kbits per second DS2506S 8-Pin SOIC Package Overdrive mode boosts communication speed to 142 kbits per second 8-bit family code specifies DS2506 communications requirements to reader Presence detector acknowledges when the reader first applies voltage Low cost PR35 or 8-pin SOIC surface mount package Reads over a wide voltage range of 2.8V to 6.0V from -40C to +85C programs at 11.5V to 12.0V from -40C to +50C 1 of 25 062100 GND DATA NCDS2506 SILICON LABEL DESCRIPTION The DS2506 64Kb Add-Only Memory identifies and stores relevant information about the product to which it is associated. This lot or product specific information can be accessed with minimal interface, for example a single port pin of a microcontroller. The DS2506 consists of a factory-lasered registration number that includes a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Family Code (0FH) plus 64Kb of user-programmable EPROM. The power to program and read the DS2506 is derived entirely from the 1-Wire communication line. Data is transferred serially via the 1-Wire protocol which requires only a single data lead and a ground return. The entire device can be programmed and then write- protected if desired. Alternatively, the part may be programmed multiple times with new data being appended to, but not overwriting, existing data with each subsequent programming of the device. Note: Individual bits can be changed only from a logical 1 to a logical 0, never from a logical 0 to a logical 1. A provision is also included for indicating that a certain page or pages of data are no longer valid and have been replaced with new or updated data that is now residing at an alternate page address. This page address redirection allows software to patch data and enhance the flexibility of the device as a stand-alone database. The 48-bit serial number that is factory-lasered into each DS2506 provides a guaranteed unique identity which allows for absolute traceability. The PR35 and SOIC packages provide a compact enclosure that allows standard assembly equipment to handle the device easily for attachment to printed circuit boards or wiring. Typical applications include storage of calibration constants, maintenance records, asset tracking, product revision status and access codes. OVERVIEW The block diagram in Figure 1 shows the relationships between the major control and memory sections of the DS2506. The DS2506 has three main data components: 1) 64-bit lasered ROM, 2) 65536-bits EPROM Data Memory, and 3) 2816-bits EPROM Status Memory. The device derives its power for read operations entirely from the 1-Wire communication line by storing energy on an internal capacitor during periods of time when the signal line is high and continues to operate off of this parasite power source during the low times of the 1-Wire line until it returns high to replenish the parasite (capacitor) supply. During programming, 1-Wire communication occurs at normal voltage levels and then is pulsed momentarily to the programming voltage to cause the selected EPROM bits to be programmed. The 1-Wire line must be able to provide 12 volts and 10 milliamperes to adequately program the EPROM portions of the part. Whenever programming voltages are present on the 1-Wire line a special high voltage detect circuit within the DS2506 generates an internal logic signal to indicate this condition. The hierarchical structure of the 1-Wire protocol is shown in Figure 2. The bus master must first provide one of the six ROM Function Commands, 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM, 5) Overdrive-Skip ROM or 6) Overdrive-Match ROM. Upon completion of an Overdrive ROM command byte executed at regular speed, the device will enter the Overdrive mode where all subsequent communication occurs at a higher speed. These commands operate on the 64-bit lasered ROM portion of each device and can singulate a specific device if many are present on the 1-Wire line as well as indicate to the bus master how many and what types of devices are present. The protocol required for these ROM Function Commands is described in Figure 8. After a ROM Function Command is successfully executed, the memory functions that operate on the EPROM portions of the DS2506 become accessible and the bus master may issue any one of the five Memory Function Commands specific to the DS2506 to read or program the various data fields. The protocol for these Memory Function Commands is described in Figure 5. All data is read and written least significant bit first. 64-BIT LASERED ROM Each DS2506 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). The 64-bit ROM and ROM Function Control section allow the DS2506 to operate as a 1-Wire device and 2 of 25