NXP Semiconductors MC68306EH16B

Overview

MC68306EH16B from Motorola is a fully integrated 68EC000-based microcontroller unit with on-chip DRAM controller, dual-channel UART (68681-compatible), eight programmable chip selects, interrupt controller, 16-bit timer/counter, JTAG boundary-scan test interface, and bus watchdog timer. It operates at 16.67 MHz, supports 4-Gbyte linear addressing, and targets embedded control systems requiring high integration and 68000-class code compatibility.

For engineers reviewing the MC68306EH16B datasheet, MC68306EH16B pinout, MC68306EH16B application, or MC68306EH16B equivalent, key selection considerations include its 128-pin QFP package, 5 V ±5% supply, 24-bit address/16-bit data bus, zero-wait-state DRAM interface for 80-ns devices, and IEEE 1149.1 compliance for production testability.

Technical Context

The MC68306EH16B integrates an EC000 core identical to the MC68EC000, delivering 2.4 MIPS at 16.67 MHz with full MC68000 instruction set compatibility and supervisor/user mode protection. Its on-chip peripherals include two independent UART channels with baud rate generators, 4-byte receive/2-byte transmit FIFOs, and full modem control signals (RTS/CTS per channel).

The DRAM controller supports up to 64 Mbytes using 16M×1 DRAMs with CAS-before-RAS refresh, while eight programmable chip selects provide configurable 1-Mbyte or 16-Mbyte memory spaces across the full 4-Gbyte address range. The integrated 16-bit timer/counter operates in timer or counter mode for periodic interrupts, event counting, or system watchdog functions.

Key Specifications

Pinout & Package

The MC68306EH16B is housed in a 128-pin plastic quad flat pack (QFP) with gull-wing leads and 0.8 mm pitch. Pin assignments are defined by functional groups including address/data bus (A19–A16, D15–D0), control signals (AS, R/W, UDS, LDS), DRAM interface (RAS0/RAS1, CAS0/CAS1), UART I/O (RxDA/TxDA, RxDB/TxDB), parallel ports (PA0–PA7, PB0–PB7), interrupt lines (IRQ1–IRQ7), chip selects (CS0–CS7), and JTAG test interface (TCK, TMS, TDI, TDO, TRST).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68332ACF16 and MC68340RC25, the MC68306EH16B uniquely balances DRAM integration, dual UART flexibility, and 68000 software compatibility - making it optimal for cost-sensitive, memory-intensive embedded controllers where upgrade path to newer M68300 derivatives is not required.

Availability

MC68306EH16B is available at Aetrix Electronics and suitable for industrial PLCs, telecom line cards, medical diagnostic instruments, and avionics data concentrators requiring stable component supply and long-term obsolescence management.

Supply support for MC68306EH16B 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

Motorola Semiconductor (now part of NXP Semiconductors) was a pioneering developer of 68000-family microprocessors and embedded controllers, known for robust industrial-grade silicon and comprehensive toolchain support.

The MC68306EH16B belongs to the M68300 family of integrated processors designed specifically for embedded control applications requiring high functional integration, code compatibility with legacy 68000 software, and reduced board-level complexity.

FAQ

What is the maximum DRAM capacity supported by the MC68306EH16B?

The MC68306EH16B supports up to 64 Mbytes of DRAM using 16M×1 devices with its integrated DRAM controller. This is achieved through two independent RAS banks, each supporting up to 16 DRAM chips, and programmable CAS-before-RAS refresh timing. The controller provides zero-wait-state access to 80-ns DRAMs, ensuring efficient memory bandwidth for the MC68306EH16B's 16.67 MHz bus cycle.

Does the MC68306EH16B support full 32-bit addressing?

Yes, the MC68306EH16B implements a full 32-bit linear address space (4 Gbytes) via its EC000 core, though only 24 address lines (A0–A23) are physically exported. The upper address bits (A24–A31) are handled internally for instruction fetch and supervisor-mode operations. External peripherals and memory are mapped within the 4-Gbyte space using the eight programmable chip selects, allowing flexible placement of resources such as ROM, SRAM, and I/O registers - all accessible by the MC68306EH16B without address translation hardware.

Is the MC68306EH16B pin-compatible with other M68300 family members?

No, the MC68306EH16B is not pin-compatible with other M68300 family members such as the MC68332 or MC68340. While sharing architectural similarities and some signal naming conventions, the MC68306EH16B uses a unique 128-pin QFP pinout optimized for its specific peripheral set - including dedicated DRAM control signals (RAS0/RAS1, CAS0/CAS1), dual UART I/O, and eight chip selects. Substitution requires PCB redesign due to differing pin allocations and electrical timing requirements.

What development tools are compatible with the MC68306EH16B?

The MC68306EH16B is fully compatible with standard 68000 development ecosystems, including Motorola's own M68K assembler and linker toolchains, third-party C compilers (e.g., GCC-m68k), and real-time operating systems such as VxWorks, pSOS+, and RTEMS. Its JTAG interface supports debugging via Motorola/Freescale BDM pods and compatible ICE tools. The MC68306EH16B also runs unmodified code written for MC68000 and MC68EC000 platforms, enabling reuse of existing drivers, bootloaders, and application firmware.

What is the operating temperature range for the MC68306EH16B?

The MC68306EH16B is specified for commercial operation from 0°C to +70°C ambient temperature. It requires a regulated 5.0 V ±5% supply voltage and features twenty dedicated power and ground pins to minimize ground bounce and ensure stable operation across its full temperature range. Thermal design should account for its typical power dissipation of approximately 1.2 W under active load, with derating recommended above 50°C ambient for long-term reliability in the MC68306EH16B.