NXP Semiconductors SCC68681C1A44,518

Overview

SCC68681C1A44,518 from NXP Semiconductors (formerly Philips Semiconductors) is a dual-channel CMOS universal asynchronous receiver/transmitter (DUART) providing two independent full-duplex serial communication channels in a single PLCC44 package. It supports programmable data formats (5–8 data bits, odd/even/no parity, 1/1.5/2 stop bits), independent baud rate selection per channel (up to 115.2 kbaud), and quadruple-buffered receivers for reduced overrun risk in interrupt-driven systems - deployed in industrial control backplanes and legacy embedded terminal interfaces.

For engineers reviewing the SCC68681C1A44,518 datasheet, SCC68681C1A44,518 pinout, SCC68681C1A44,518 application, or SCC68681C1A44,518 equivalent, key selection criteria include its S68000 bus compatibility, 16-bit programmable counter/timer, dual-channel flow control via RTS/CTS, on-chip crystal oscillator, and support for multidrop wake-up mode with address/data tagging.

Technical Context

The SCC68681C1A44,518 implements two fully independent UART channels (A and B), each with separate mode registers (MR1/MR2), status registers (SRA/SRB), and command registers (CRA/CRB). Each channel's receiver and transmitter operate at independently selectable baud rates derived from either the on-chip crystal oscillator (3.6864 MHz nominal), external clock inputs (X1/CLK, IP2–IP5), or a 16-bit programmable counter/timer.

Its timing architecture includes a dedicated baud rate generator producing 22 fixed rates (50–115.2 kbaud), plus non-standard user-defined rates via timer-derived clocks. The receiver employs 16× oversampling with start-bit detection, framing/parity/error strobing at character boundaries, and a 3-deep FIFO with FFULL/RxRDY status flags - all configurable via the ACR, OPCR, and mode registers.

Key Specifications

Pinout & Package

SCC68681C1A44,518 is housed in a plastic leaded chip carrier (PLCC44) package with J-lead geometry, 44 pins, and 1.27 mm pitch - designed for through-hole or surface-mount assembly in high-reliability industrial PCBs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual UART applications.

Compared with SCC68681C1N40, the SCC68681C1A44,518 offers superior board-space efficiency and thermal performance in surface-mount layouts; versus TL16C550CP, it delivers integrated dual-channel operation with hardware-assisted flow control and multidrop intelligence - reducing BOM cost and real-time CPU load in distributed control systems.

Availability

SCC68681C1A44,518 is available at Aetrix Electronics and suitable for industrial serial backplanes, legacy terminal interfaces, SCADA remote terminal units, and embedded modem control requiring stable component supply across extended product lifecycles.

Supply support for SCC68681C1A44,518 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

NXP Semiconductors is a global semiconductor leader specializing in secure connectivity solutions for automotive, industrial, and IoT applications - formed from the spin-off of Philips Semiconductors in 2006.

The SCC68681 series belongs to NXP's legacy communications interface portfolio, engineered specifically for robust, long-lifecycle embedded systems requiring deterministic serial I/O with minimal software overhead and hardware-level flow control.

FAQ

What is the maximum supported baud rate for SCC68681C1A44,518?

The SCC68681C1A44,518 supports a maximum baud rate of 115.2 kbaud per channel, achievable using the on-chip baud rate generator or external clock inputs. This rate is confirmed in the Philips product data sheet (2004 Apr 06) and applies to both Channel A and Channel B independently. The device also supports non-standard rates up to this limit via its 16-bit programmable counter/timer, enabling precise synchronization with legacy modems and industrial protocols.

Does SCC68681C1A44,518 include an on-chip oscillator?

Yes, the SCC68681C1A44,518 integrates an on-chip crystal oscillator that operates directly from a 3.6864 MHz crystal connected between X1/CLK and X2 pins. This eliminates the need for external oscillator circuitry and ensures stable timing for baud generation, counter/timer operation, and internal logic sequencing. The oscillator is explicitly documented in the "Timing Circuits" section of the official product data sheet.

How does the receiver FIFO work in SCC68681C1A44,518?

The SCC68681C1A44,518 features a 3-character deep FIFO buffer for each receiver channel, implemented as a first-in-first-out stack with associated status flags (RxRDY, FFULL). Data is loaded from the shift register into the topmost empty position; reading the RHR pops the FIFO and clears the corresponding status bits. The FIFO preserves data integrity during interrupt latency spikes and is explicitly described in the "Receiver FIFO" subsection of the product data sheet.

Can SCC68681C1A44,518 operate in multidrop networks?

Yes, the SCC68681C1A44,518 supports multidrop wake-up mode via programmable address/data bit tagging (MR1A[4:3]/MR1B[4:3] = '11'). In this mode, receivers monitor incoming data streams continuously and assert RxRDY only upon detecting an address-tagged character - allowing slave nodes to remain in low-power state until explicitly addressed. This functionality is fully specified in the "Multidrop Mode" section of the official datasheet.

What package type is used for SCC68681C1A44,518?

The SCC68681C1A44,518 uses a plastic leaded chip carrier (PLCC44) package with 44 J-leads and SOT187-2 footprint. This surface-mount package is explicitly listed in the "Ordering Information" table of the Philips product data sheet and is distinct from the DIP40 variant (SCC68681C1N40). Its thermal and mechanical characteristics are optimized for industrial PCB assembly and long-term reliability.