NXP Semiconductors P89C668HBA/00,512

Overview

P89C668HBA/00,512 from Philips Semiconductors is a single-chip 8-bit Flash microcontroller based on the 80C51 architecture, featuring 64 KB ISP/IAP Flash program memory, 8 KB RAM, four 8-bit I/O ports, three 16-bit timers, enhanced UART with framing error detection and automatic address recognition, I²C interface, and Programmable Counter Array (PCA) supporting PWM and capture/compare functions - deployed in industrial motor control and IPMI-compliant embedded systems.

For engineers reviewing the P89C668HBA/00,512 datasheet, P89C668HBA/00,512 pinout, P89C668HBA/00,512 application, or P89C668HBA/00,512 equivalent, key selection criteria include 6-clock-cycle execution mode (20 MHz max), PLCC-44 package with verified pin mapping, ISP/IAP programmability via UART boot loader, I²C slave/master capability on P1.6/P1.7, and hardware reset timing compatibility with 80C51 systems.

Technical Context

The P89C668HBA/00,512 implements an accelerated 80C51 CPU core with dual clock modes: default 6-clock-per-machine-cycle operation (20 MHz max, 40 MHz equivalent performance) and optional factory-configured 12-clock mode (33 MHz max). It integrates a full-duplex enhanced UART with framing error detection and automatic address recognition, enabling robust serial communication in noisy environments.

Its on-chip peripherals include a 5-level nested interrupt structure with four priority levels and eight sources, a 5-channel PCA supporting PWM generation and edge-triggered capture/compare, and I²C interface logic compliant with standard I²C bus specification (excluding low-speed mode), implemented on open-drain P1.6/SCL and P1.7/SDA pins requiring external pull-ups.

Key Specifications

Pinout & Package

Package: Plastic Leaded Chip Carrier (PLCC), 44-pin, SOT187-2 footprint, operating temperature range 0°C to +70°C, supply voltage 4.5 V to 5.5 V.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit microcontroller applications.

Compared with AT89C51ED2-RLTUM and STC89C52RC-PD, the P89C668HBA/00,512 uniquely balances ISP/IAP flexibility, integrated I²C and PCA peripherals, and 20 MHz 6-clock performance - making it optimal for upgradable industrial controllers where hardware resources and field serviceability are both critical.

Availability

P89C668HBA/00,512 is available at Aetrix Electronics and suitable for industrial motor control, IPMI baseboard management, and legacy PLC I/O modules requiring stable component supply and long-term lifecycle support.

Supply support for P89C668HBA/00,512 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

Philips Semiconductors (now NXP Semiconductors) is a global leader in high-reliability mixed-signal ICs for industrial and automotive applications.

The P89C66x family was designed specifically for upgrade paths from legacy 80C51 systems - delivering enhanced Flash programmability, real-time peripheral integration (PCA, I²C), and deterministic timing for industrial automation and embedded control.

FAQ

What is the maximum operating frequency of the P89C668HBA/00,512 and how does clock mode affect performance?

The P89C668HBA/00,512 operates up to 20 MHz in its default 6-clock-per-machine-cycle mode (delivering 40 MHz equivalent throughput vs. standard 80C51), or up to 33 MHz in optional 12-clock mode. The 6-clock mode is factory-default and provides twice the instruction throughput of conventional 80C51 cores. Once configured for 12-clock mode via EPROM programmer, the device cannot revert to 6-clock mode. Both modes maintain full 80C51 instruction timing compatibility.

Does the P89C668HBA/00,512 support in-system programming via UART, and what boot loader mechanism enables this?

Yes, the P89C668HBA/00,512 supports UART-based In-System Programming (ISP) using a factory-programmed boot loader stored in ROM. This loader executes on power-up or reset when EA/VPP is held low, allowing serial download of new firmware directly into Flash memory without external programming hardware. The process requires no user code in Flash and works independently of the application firmware running in the P89C668HBA/00,512.

How is the I²C interface implemented on the P89C668HBA/00,512, and what hardware constraints apply to P1.6 and P1.7?

The P89C668HBA/00,512 implements I²C on P1.6 (SCL) and P1.7 (SDA) as open-drain outputs - unlike standard 80C51 ports, these pins lack internal pull-ups and require external 2.2–10 kΩ pull-up resistors to VCC. The on-chip SIO1 logic handles START/STOP generation, arbitration, and status tracking autonomously via S1CON, S1STA, S1DAT, and S1ADR registers - enabling full master/slave operation without CPU bit-banging overhead.

What power management modes does the P89C668HBA/00,512 support, and how do they differ in terms of peripheral retention and wake-up sources?

The P89C668HBA/00,512 supports three low-power modes: Idle (CPU halted, peripherals active, wake via interrupt/reset), Stop Clock (oscillator running but gated, all state preserved), and Power-Down (oscillator stopped, RAM/SFRs retained down to 2.0 V, wake via reset or level-sensitive INT0/INT1). In Power-Down mode, external interrupts must be configured as level-sensitive and held low to restart the oscillator before returning to normal operation.

Can the P89C668HBA/00,512 generate PWM signals, and which hardware module enables this functionality?

Yes, the P89C668HBA/00,512 generates hardware PWM using its five-channel Programmable Counter Array (PCA). Each channel (CEX0–CEX4) can be independently configured for PWM output with adjustable duty cycle and frequency via CCAPMn and CCAPnL/H registers. The PCA operates independently of the CPU - enabling precise, jitter-free PWM for motor control or LED dimming without consuming instruction cycles.