The **DS1995** is a 16-Kbit Memory iButton developed by Maxim Integrated (now part of Analog Devices). It acts as a rugged, portable data carrier that communicates via the proprietary 1-Wire protocol. --- ## 1. Key Specifications The DS1995 is essentially a non-volatile memory chip housed in a durable stainless steel "can." | Feature | Specification | | :--- | :--- | | **Memory Capacity** | 16 Kilobits (2048 Bytes) | | **Memory Type** | NVRAM (Non-Volatile RAM) | | **Communication Interface** | 1-Wire (Data + Ground) | | **Unique Address** | Factory-lasered 64-bit ROM ID | | **Operating Voltage** | 2.8V to 6.0V | | **Data Retention** | Over 10 years (Internal Lithium Battery) | | **Durability** | Water-resistant, shock-proof, stainless steel | --- ## 2. Internal Electronic Architecture The DS1995 consists of several core electronic modules working in tandem: ### A. 64-Bit ROM ID Each device contains a unique, unalterable serial number. This allows multiple iButtons to share a single data bus (Multi-drop) and ensures traceability. ### B. NVRAM (Non-Volatile RAM) Unlike EEPROM, which has limited write cycles, the DS1995 uses SRAM backed by an internal lithium energy source. * **Write Speed:** Extremely fast (no "write cycle" delay). * **Endurance:** Virtually unlimited write cycles. * **Structure:** The 16Kb memory is organized into 64 pages of 256 bits each. ### C. Scratchpad To ensure data integrity during transmission, the DS1995 uses a **32-byte scratchpad**. Data is first written to the scratchpad, verified by the host, and only then copied to the main memory. --- ## 3. Communication Protocol (1-Wire) The electronic interface is simplified to just two contacts: the **Lid** (data/signal) and the **Base** (ground). ```c // Simplified 1-Wire Communication Flow: 1. Reset Pulse (Master) -> Presence Pulse (DS1995) 2. ROM Command (Match ID or Skip ROM) 3. Memory Function Command (Read/Write Scratchpad) 4. Data Transfer (8-bit blocks) ``` --- ## 4. Physical Form Factor: The F5 MicroCan The electronics are protected by a "button" package: * **Material:** Stainless Steel. * **Mounting:** Can be attached to key fobs, ID badges, or equipment. * **Environmental:** Designed to withstand harsh environments where traditional RFID cards or flash drives might fail. --- ## 5. Typical Applications * **Asset Tracking:** Storing maintenance logs on heavy machinery. * **Access Control:** Storing user credentials or biometric templates. * **Electronic Cash:** Used in closed-loop payment systems (e.g., transit tokens). * **Travel Records:** Storing route data for logistics and fleet management. ---