Product Overview
Used Enhanced Programmable Communications Interface USART - SCN2661BC1N28
Product Condition
Used, clean working pull from lightly used lab equipment. 28-pin plastic DIP package with straight leads and clear markings. Removed carefully from operational hardware; no accessories included.
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Product Overview
Signetics SCN2661BC1N28 is an Enhanced Programmable Communications Interface (EPCI), a feature-rich synchronous and asynchronous USART designed for 8-bit and 16-bit microprocessor systems. This “B” version is configured for a 4.9152 MHz master clock when using its internal baud rate generator. Housed in a 28-pin PDIP package, it operates from a standard 5V TTL supply and interfaces directly with parallel system buses.
Unlike basic UARTs, the SCN2661 supports BISYNC and other synchronous protocols in hardware, reducing CPU overhead in industrial and laboratory systems. Integrated loopback modes allow internal and line-level diagnostics without external test equipment. Originally used in instrumentation, terminals, and embedded controllers, it remains essential for maintaining and restoring legacy serial hardware.
Key Features
- Device: SCN2661BC1N28 Enhanced Programmable Communications Interface
- Package: 28-pin Plastic Dual In-Line (PDIP)
- Baud Version: “B” variant for 4.9152 MHz clock operation
- Supply Voltage: 4.75V to 5.25V (5V nominal)
- Asynchronous modes with selectable stop bits
- Synchronous protocol support including BISYNC
- Automatic DLE handling and SYN insertion
- Local and remote loopback diagnostic modes
- TTL-compatible logic levels
- Data rates up to 1 Mbps in external clock mode
Applications
- Restoration of vintage microprocessor-based systems
- Industrial serial communication controllers
- Laboratory instrumentation interfaces
- Legacy terminal and data acquisition hardware
- Retrocomputing and SBC projects
- Custom embedded systems requiring hardware protocol handling
- Replacement for failed SCN2661B devices in existing boards
Frequently Asked Questions
What does the “B” in SCN2661BC1N28 mean?
The “B” designates the baud rate generator version intended for use with a 4.9152 MHz master clock. It is not directly interchangeable with the “A” or “C” versions if the system depends on the internal baud rate generator.
Is this compatible with the older 2651?
Yes. The SCN2661 is pin-compatible with the 2651 family, but offers enhanced baud rate flexibility and additional protocol support.
What supply voltage does it require?
It operates from a regulated 5V supply, typically within 4.75V to 5.25V. Absolute maximum ratings must not be exceeded.
Does it support both synchronous and asynchronous communication?
Yes. It supports asynchronous modes with configurable stop bits and synchronous modes including BISYNC with hardware-assisted control features.
Is ESD handling important for this IC?
Yes. As an NMOS-era device, it should be handled using proper anti-static precautions during installation and storage.
Before USB and integrated serial controllers, communication depended on dedicated silicon like this. If you are keeping a legacy system alive, this chip still speaks its language.
