Analog Devices Inc./Maxim Integrated DS1216E

Overview

DS1216E from Maxim Integrated is a SmartWatch ROM socket - a 28-pin, 600-mil DIP intelligent socket integrating a real-time clock (RTC), lithium backup power source, and ROM interface logic. It supports 64K x 8 to 256K x 8 ROM densities, maintains time/date with ±1 minute/month accuracy at +25°C, and uses A2/A0 address pins for RTC register access. It is used in legacy embedded systems requiring battery-backed timekeeping without RAM volatility concerns.

For engineers reviewing the DS1216E datasheet, DS1216E pinout, DS1216E application, or DS1216E equivalent, this page provides verified technical context, validated pin functions, confirmed ROM-specific operation mode, documented timing register access protocol, and real-world supply-chain availability for industrial and medical instrumentation designs.

Technical Context

The DS1216E implements a dedicated ROM-access RTC controller using A2 and A0 as serial command inputs for 64-bit pattern recognition - distinct from the RAM-access method that uses DQ0. Its internal lithium cell powers only the RTC circuitry, not memory retention, and remains electrically disconnected until first VCC application to preserve freshness.

It features automatic leap-year compensation valid through 2100, BCD-formatted time registers (seconds to years), 12-/24-hour mode selection via bit 7 of the hour register, and oscillator enable/disable control via bit 5 of the day register - all accessible only after successful pattern match. The RST pin has an internal pullup and can be disabled by cutting the trace to pin 13 on the controller.

Key Specifications

Pinout & Package

DS1216E is housed in a 28-pin, 600-mil-wide dual-in-line package (DIP) with gas-tight socket contacts. Dimensions: 1.405" × 0.705" × 0.445" (35.7 × 17.9 × 11.3 mm). RoHS-compliant; shipped with lithium energy source disconnected until first power-up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ROM-integrated RTC applications.

Compared with DS1216F, DS1216E saves PCB area and simplifies layout for 64K–256K ROM systems; compared with DS12887A, it eliminates RAM contention and reduces software complexity by decoupling timekeeping from memory access.

Availability

DS1216E is available at Aetrix Electronics and suitable for medical infusion pumps, industrial PLC HMIs, and legacy point-of-sale terminals requiring stable component supply, long-lifecycle support, and RoHS-compliant 28-pin DIP packaging.

Supply support for DS1216E includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for industrial, medical, and communications applications.

The DS1216E belongs to the SmartWatch family - engineered specifically to embed RTC functionality into existing ROM-based embedded systems without modifying memory architecture or adding external components.

FAQ

What is the primary function of the DS1216E in a system design?

The DS1216E serves as a SmartWatch ROM socket - a 28-pin DIP device that integrates a real-time clock (RTC) with ROM interface logic. Unlike RAM variants, it uses A2 and A0 pins to access time registers and maintains time/date solely via its embedded lithium cell, without backing up ROM data. Its design purpose is to add battery-backed timekeeping to legacy ROM-based systems while preserving full 8-bit parallel ROM data paths and requiring zero changes to existing memory addressing schemes. DS1216E enables timestamping, logging, and calendar functions in medical, industrial, and POS equipment where external RTCs would increase BOM cost and PCB complexity.

How does the DS1216E differ from the DS1216B/C/D/H variants?

The DS1216E is explicitly designated as a SmartWatch ROM socket, whereas DS1216B/C/D/H are SmartWatch RAM sockets. This distinction is fundamental: DS1216E uses A2 and A0 for RTC register access and provides no nonvolatile RAM controller circuitry, while RAM variants use DQ0 and include NV RAM switching logic. DS1216E supports 64K x 8 to 256K x 8 ROM densities in a 28-pin package, whereas DS1216F (ROM) and DS1216D/H (RAM) use 32-pin packages for higher densities. Pin functions like VCCB and VCCD are unused in DS1216E, confirming its ROM-only role per Maxim's Selector Guide and ordering table.

What is the correct procedure to access the RTC registers on the DS1216E?

To access RTC registers on the DS1216E, perform a 64-bit pattern match using A2 and A0: first execute one read cycle with A2 high to reset the comparison pointer, then execute 64 consecutive write cycles with A2 low and A0 toggling according to the hex pattern C5h, 3Ah, A3h, 5Ch, C5h, 3Ah, A3h, 5Ch (LSB to MSB). After match success, the next 64 cycles read or write the eight BCD-formatted time registers (hundredths/sec to year) via DQ0, controlled by OE (read) or WE (write). DS1216E requires no RST assertion or DQ0-based sequences - its ROM-specific protocol avoids interfering with ROM data transfers.

Does the DS1216E provide battery backup for the connected ROM device?

No, the DS1216E does not provide battery backup for the connected ROM device. Its embedded lithium energy source powers only the RTC circuitry - timekeeping and register retention - and is electrically disconnected from the ROM's VCC pin. The "SmartWatch ROM" designation means the socket uses the lithium cell exclusively for maintaining time/date, unlike SmartWatch RAM variants (e.g., DS1216B) which switch the lithium source to back up both RTC and SRAM. DS1216E's VCC pin supplies switched power to the ROM only during normal operation; during power loss, ROM contents are volatile, but RTC registers remain intact for ≥10 years.

What is the expected data retention time for the DS1216E's RTC function?

The DS1216E provides ≥10 years of RTC data retention when powered solely by its embedded lithium cell, based on Maxim's specification under backup power conditions (VCC < VTP, TA = 0°C to +70°C). This assumes proper first-power-up activation (which electrically connects the lithium source) and adherence to handling precautions - notably avoiding water washing or ultrasonic cleaning, which can discharge the cell. The 10-year figure is derived from the lithium cell's capacity and the RTC's typical 10µA backup current draw, and is validated across the full operating temperature range. DS1216E's freshness seal ensures full retention potential from shipment, with no shelf-life degradation prior to initial power application.