The W78C33B microcontroller is an 8-bit microcontroller that offers a wider frequency range than most 8-bit microcontrollers on the market. It is functionally compatible with the industry standard 80C32 microcontroller series, with the exception of an extra 4-bit bit-addressable I/O port (Port 4). The microcontroller features four 8-bit bidirectional parallel ports, three 16-bit timer/counters, and a serial port. These peripherals are supported by a six-source, two-level interrupt capability. It has 256 bytes of RAM and supports ROMless operation. The microcontroller also has two power reduction modes: idle mode and power-down mode, which can be selected through software. The idle mode turns off the processor clock while allowing for continued peripheral operation, while the power-down mode stops the crystal oscillator for minimum power consumption. The external clock can be stopped at any time and in any state without affecting the processor.
The W78C33B is an 8‑bit CMOS microcontroller with a wide frequency range and full static design. It offers four 8‑bit bidirectional ports, an extra 4‑bit port, three 16‑bit timer/counters, a full‑duplex serial port, and six‑source, two‑level interrupt capability. The device supports ROMless operation and two software‑selectable power‑reduction modes (idle and power‑down).
Key features include 256 bytes of on‑chip RAM, 64 KB program and data address spaces, built‑in power management, and multiple package options (PLCC‑44, QFP‑44, TQFP‑44). The datasheet details pin assignments, electrical characteristics, timing diagrams, and a typical application circuit.
| Operating Voltage (VDD) | 4.5 V – 5.5 V |
|---|---|
| Operating Current (no load) | ≤ 20 mA |
| Idle Current (VDD = 5.5 V) | ≤ 6 mA |
| Power‑down Current (VDD = 5.5 V) | ≤ 50 µA |
| Input Low Voltage (P0‑P4) | 0 V – 0.8 V (VDD = 4.5 V) |
| Input High Voltage (P0‑P4) | 2.4 V – 5.5 V (VDD = 5.5 V) |
| Output Low Voltage (P1‑P4) | ≤ 0.45 V (IOL = +2 mA) |
| Output High Voltage (P1‑P4) | ≥ 2.4 V (IOH = ‑100 µA) |
The device operates from 4.5 V to 5.5 V.
It has four 8‑bit bidirectional ports and an additional 4‑bit port (Port 4).
The microcontroller supports an idle mode that stops the processor clock while keeping peripherals active, and a power‑down mode that stops all clocks including the oscillator.
The device can operate up to 40 MHz.