Analog Devices Inc./Maxim Integrated DS1481S+

Overview

DS1481S+ from Maxim Integrated is a dedicated 1-Wire® bus master timing generator for parallel-port-based host interfaces, supporting standard-speed (8 μs sample) and overdrive-speed (2 μs sample) communication, 3V–5.5V operation, and cascaded multi-device configurations. It enables microcontroller or PC parallel port interfacing with Dallas Semiconductor 1-Wire devices in short-network (<3 inch) embedded instrumentation and sensor systems.

For engineers reviewing the DS1481S+ datasheet, DS1481S+ pinout, DS1481S+ application, or DS1481S+ equivalent, key selection considerations include its dual busy-signal arbitration (O1/BSY1 & O2/BSY2), transparent/EPP/ECP mode toggle sequence, ENI-triggered time-slot execution, and printer coexistence logic for legacy parallel port integration.

Technical Context

The DS1481S+ implements a synchronous 1-Wire timing engine that offloads precise bit- and reset-slot generation from the host processor using D/CLK and RES input state latching on ENI falling edge. Its dual open-drain busy outputs (O1/BSY1, O2/BSY2) provide asynchronous status signaling while enabling concurrent print spooler operation.

It supports two operational modes: transparent mode (direct EPP/ECP signal pass-through via transmission gates) and normal mode (1-Wire I/O), toggled by four consecutive overdrive commands. Overdrive mode (OD=1) reduces tSIO from 8 μs to 2 μs and tBLB from 60 μs to 6 μs without altering I/O line behavior during mode switching.

Key Specifications

Pinout & Package

DS1481S+ is housed in a 14-pin small-outline integrated circuit (SOIC) package with 150-mil body width and standard 0.050″ lead pitch. Pin 1 is VCC; pins 7 and 8 are NC and GND respectively; all inputs feature internal 50 kΩ weak pull-ups except I/O (open-drain).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-Wire bus master applications.

Compared with DS2480B+ and DS9490R, the DS1481S+ uniquely preserves legacy parallel port infrastructure, enables printer coexistence via dual busy signaling, and supports hardware-cascaded multi-master topologies-making it irreplaceable in retrofit industrial PC environments where USB is unavailable or prohibited.

Availability

DS1481S+ is available at Aetrix Electronics and suitable for industrial sensor hubs, legacy PC peripheral adapters, microcontroller-based data loggers, and multi-node environmental monitors requiring stable component supply and long-term obsolescence management.

Supply support for DS1481S+ 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) is a semiconductor company specializing in analog, mixed-signal, and high-reliability ICs for industrial, communications, and computing applications.

The DS1481S+ belongs to Maxim's 1-Wire interface product line, designed specifically to simplify host-side 1-Wire protocol implementation in resource-constrained parallel-port and microcontroller systems.

FAQ

What is the primary function of the DS1481S+ in a 1-Wire system?

The DS1481S+ serves as a dedicated 1-Wire bus master timing generator that offloads precise reset and bit-slot timing from the host processor. It interprets D/CLK and RES inputs upon ENI activation to execute standardized 1-Wire transactions-including presence detection, read/write, and overdrive mode switching-while asserting O1/BSY1 and O2/BSY2 to signal completion. This enables deterministic timing without software bit-banging, making DS1481S+ essential for reliable 1-Wire communication in parallel-port or microcontroller-based systems.

How does the DS1481S+ support coexistence with parallel port printers?

The DS1481S+ supports parallel port printer coexistence through its dual-input/dual-output architecture: I1 and I2 accept the printer's BUSY and SELECT OUT signals, while O1/BSY1 and O2/BSY2 propagate those states when idle. During 1-Wire activity, the DS1481S+ asserts both outputs low to indicate busy, then restores them to I1/I2 states post-transaction. In transparent mode, it passes EPP/ECP signals directly-ensuring full printer functionality remains intact while enabling concurrent 1-Wire access without hardware conflict.

What is the significance of the "Not Recommended for New Design" notice on the DS1481S+ datasheet?

The "Not Recommended for New Design" status reflects Maxim's strategic shift toward USB-based 1-Wire solutions (e.g., DS2480B+, DS9490R) and discontinuation of parallel-port-focused development. However, DS1481S+ remains fully qualified, in active production, and supported for legacy system maintenance, repair, and obsolescence-sensitive industrial deployments. Aetrix Electronics maintains inventory and supply chain continuity for DS1481S+ to serve ongoing needs in installed base equipment where parallel port infrastructure is fixed and irreplaceable.

Can multiple DS1481S+ devices be used together, and how is cascading implemented?

Yes, DS1481S+ devices can be cascaded to expand 1-Wire port count or isolate subnets. Cascading uses ENO of one device connected to ENI of the next, with O1/BSY1 and O2/BSY2 of the upstream unit wired to I1 and I2 of the downstream unit. The last device detects absence of upstream busy signaling and disables ENO, preventing false printer line-feed assertions. This daisy-chain topology allows up to four DS1481S+ units per parallel port while maintaining independent timing control and busy arbitration per node.

What are the key timing parameters that differentiate standard and overdrive modes in the DS1481S+?

In standard mode (OD=0), DS1481S+ uses tSIO = 8 μs for bit-slot sampling and tBLB = 60 μs for busy assertion during bit operations; in overdrive mode (OD=1), these reduce to tSIO = 2 μs and tBLB = 6 μs. Reset timing similarly scales: tBLR drops from 960 μs to 96 μs. These values are hard-coded in silicon and require no host recalibration-only a four-command OD toggle sequence. Overdrive mode is fully backward-compatible and maintains identical I/O waveform shapes, ensuring interoperability with mixed-standard/overdrive 1-Wire networks.