NXP Semiconductors MC68EN302AG20BT

Overview

MC68EN302AG20BT from Freescale is an integrated multiprotocol processor combining a 68000-compatible CPU core, three serial communication controllers (SCCs), a full IEEE 802.3-compliant Ethernet controller, DRAM controller, and JTAG debug interface - all in a single 144-pin TQFP package operating at 20 MHz with 5 V supply. It targets embedded networking bridges and ISDN-to-Ethernet routers requiring deterministic real-time serial + Ethernet co-processing.

For engineers reviewing the MC68EN302AG20BT datasheet, MC68EN302AG20BT pinout, MC68EN302AG20BT application, or MC68EN302AG20BT equivalent, key selection criteria include its dual 128-byte Ethernet FIFOs, dedicated transmit/receive DMA channels, on-chip descriptor RAM, glueless DRAM control with RAS/CAS support, and IEEE 1149.1 compliance for boundary-scan testability.

Technical Context

The MC68EN302AG20BT extends the MC68302 architecture with a fully integrated Ethernet MAC layer compliant to IEEE 802.3, supporting 10 Mbps half-duplex and 20 Mbps full-duplex operation. Its Ethernet controller uses two dedicated DMA channels and separate 128-byte transmit/receive FIFOs managed by a buffer descriptor control (BDC) block accessing 1152 bytes of on-chip dual-port RAM.

The DRAM controller supports two banks with independent RAS0/RAS1 and CAS0/CAS1 lines, programmable wait states (0–3), and hidden refresh - enabling zero-wait-state operation with 100 ns DRAM at 20 MHz. The module bus controller handles interrupt routing for Ethernet and DRAM peripherals while coordinating bus arbitration between internal and external masters.

Key Specifications

Pinout & Package

MC68EN302AG20BT is housed in a 144-lead thin quad flat pack (TQFP) with 0.5 mm lead pitch, low-profile construction, and standard JEDEC MO-152 footprint. Pin functions are defined across multiple I/O groups including address/data bus (A23–A1, D15–D0), peripheral control (RX/TX/RENA/CLSN/TENA/TCLK), DRAM signals (RAS0/RAS1/CAS0/CAS1/DRAMRW), and JTAG (TMS/TCK/TDO/TDI/TRST).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar integrated multiprotocol processor applications.

Compared with MC68EN302AG20BT, MC68302FC16B requires external components to achieve Ethernet connectivity and offers no DRAM control, while MC68EN360CZP25 abandons SCC-based serial protocol acceleration entirely - making MC68EN302AG20BT uniquely suited for deterministic, multi-protocol edge devices needing both legacy serial and native Ethernet in one die.

Availability

MC68EN302AG20BT is available at Aetrix Electronics and suitable for ISDN-to-Ethernet routers, remote dial-in access points, and low-end network bridges requiring stable component supply and long-term industrial lifecycle support.

Supply support for MC68EN302AG20BT 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

Freescale Semiconductor (now part of NXP Semiconductors) was a leading designer of embedded processors and analog/mixed-signal ICs for automotive, industrial, and networking markets.

The MC68EN302AG20BT belongs to Freescale's 68K-family integrated multiprotocol processor line, designed specifically to consolidate serial communications (SCCs), Ethernet, and DRAM control into a single chip for cost-sensitive, real-time edge networking equipment.

FAQ

What is the maximum Ethernet data rate supported by the MC68EN302AG20BT?

The MC68EN302AG20BT supports IEEE 802.3-compliant Ethernet at up to 10 Mbps in half-duplex mode and 20 Mbps in full-duplex mode. Its Ethernet controller includes dedicated transmit and receive DMA channels, 128-byte FIFOs, and automatic collision handling - enabling sustained throughput without CPU bus contention. This performance level is fixed in silicon and does not scale with clock frequency beyond the rated 20 MHz operation of the MC68EN302AG20BT.

Does the MC68EN302AG20BT include an integrated DRAM controller, and what memory configurations does it support?

Yes, the MC68EN302AG20BT integrates a glueless DRAM controller supporting two independent banks with RAS0/RAS1 and CAS0/CAS1 outputs. Each bank is programmable from 128 KB to 8 MB, with configurable wait states (0–3) and hidden refresh. At 20 MHz, it achieves zero-wait-state operation with 100 ns DRAM - a key design feature confirmed in Freescale's MC68EN302 documentation and directly applicable to the MC68EN302AG20BT variant.

How many serial communication channels does the MC68EN302AG20BT provide, and what protocols do they support?

The MC68EN302AG20BT provides four serial channels: three fully featured Serial Communication Controllers (SCCs) inherited from the MC68302, plus one integrated Ethernet MAC channel. The SCCs support HDLC, SDLC, Bisync, ASCII, and transparent modes - enabling ISDN, X.25, and proprietary protocol stacks. The Ethernet channel operates independently and does not affect SCC performance, as stated in the official MC68EN302 product brief and verified in its feature list.

Is the MC68EN302AG20BT compatible with JTAG boundary-scan testing, and which pins are used?

Yes, the MC68EN302AG20BT is fully compliant with IEEE 1149.1 JTAG boundary-scan. It uses five dedicated pins: TMS (Test Mode Select), TCK (Test Clock), TDO (Test Data Out), TDI (Test Data In), and TRST (Test Reset). These signals are electrically and functionally identical to standard JTAG implementations, enabling production test, debug access, and board-level interconnect verification - a confirmed capability documented in the MC68EN302 product information and pin description tables.

What package type and thermal specifications apply to the MC68EN302AG20BT?

The MC68EN302AG20BT is packaged in a 144-lead thin quad flat pack (TQFP) with 0.5 mm lead pitch and commercial temperature rating (0°C to 70°C). Its ordering suffix "G20BT" indicates 20 MHz speed grade, 5 V operation, and PV-series packaging - consistent with Freescale's MC68EN302PV20 part number designation. This package supports standard surface-mount reflow profiles and is compatible with automated assembly processes used in industrial embedded manufacturing.