Renesas M38B79FFFP#U0

Overview

M38B79FFFP#U0 from Renesas Technology Corp. is a single-chip 8-bit CMOS microcomputer based on the 740 family core, designed for embedded control in fluorescent display–driven systems. It integrates 60 KB Flash ROM, 2048 bytes RAM, a 16-channel 10-bit A-D converter, six 8-bit timers plus one 16-bit timer, and dedicated fluorescent display (FLD) control across 56 pins - enabling direct drive of multi-digit vacuum fluorescent displays in consumer audio and home appliance front panels.

For engineers reviewing the M38B79FFFP#U0 datasheet, M38B79FFFP#U0 pinout, M38B79FFFP#U0 application, or M38B79FFFP#U0 equivalent, this page delivers verified technical context, exact pin functions per I/O port group, real-world use cases in VCRs and musical instruments, and two validated alternative parts with documented functional and packaging differences.

Technical Context

The M38B79FFFP#U0 implements the standard 740-family instruction set with 71 basic machine-language instructions and supports three clock modes: high-speed (4.2 MHz, 4.0–5.5 V), middle-speed (f/4 division), and low-speed (32 kHz sub-clock, 2.7–5.5 V). Its CPU includes an 8-bit accumulator, dual 8-bit index registers (X/Y), 8-bit stack pointer with page-selectable addressing, and a 16-bit program counter.

On-chip peripherals include three serial I/O modules (SIO1 with 256-byte automatic transfer, SIO2 configurable as UART or clock-synchronized, SIO3 clock-synchronized), 14-bit PWM0 and 8-bit PWM1 outputs, integrated buzzer drivers (BUZ01/BUZ02), and a fluorescent display controller supporting up to 56 segment/common lines with 52 high-breakdown-voltage P-channel open-drain outputs.

Key Specifications

Pinout & Package

Package: 100-pin plastic QFP (100P6S-A), 0.65 mm pitch, surface-mount. Pinout conforms to Fig. 1 in original Mitsubishi documentation and is validated for M38B79FFFP#U0 as Flash memory variant of the 38B7 Group.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M38B79FFFP#U0, the M38B79MFH-XXXXFP offers identical hardware functionality at lower unit cost but lacks field-programmability, while the UPD78F0504GC-GAD-AX provides modern toolchain support and higher integration elsewhere but removes the critical FLD acceleration that defines the 38B7's value in display-centric appliances.

Availability

M38B79FFFP#U0 is available at Aetrix Electronics and suitable for VCR front panels, musical instrument UIs, and home appliance control systems requiring stable component supply, long-lifecycle support, and proven fluorescent display integration.

Supply support for M38B79FFFP#U0 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

Renesas Technology Corp. (now part of Renesas Electronics Corporation) was formed in 2003 through the merger of Hitachi and Mitsubishi Electric's semiconductor operations, specializing in microcontrollers, analog, and mixed-signal ICs for industrial and consumer applications.

The 38B7 Group - including M38B79FFFP#U0 - was developed specifically for cost-sensitive, display-intensive consumer electronics such as VCRs, audio equipment, and household appliances requiring integrated fluorescent display control and low-power operation.

FAQ

What is the Flash memory capacity and endurance rating of the M38B79FFFP#U0?

The M38B79FFFP#U0 contains 60 KB of Flash memory (61,440 bytes total, with 61,310 bytes user-accessible). It supports byte-level programming and block/batch erasing with a rated endurance of 100 program/erase cycles under specified VPP = 11.7–12.6 V conditions. This makes it suitable for infrequent firmware updates in deployed appliances but not for data logging applications.

Does the M38B79FFFP#U0 support external crystal oscillators on both main and sub-clock inputs?

Yes - the M38B79FFFP#U0 supports external crystals or ceramic resonators on both XIN/XOUT (main clock, e.g., 4.2 MHz) and XCIN/XCOUT (sub-clock, e.g., 32 kHz). The main clock includes an internal feedback resistor; the sub-clock does not, requiring external load capacitance matching per resonator datasheet.

How many high-breakdown-voltage output pins does the M38B79FFFP#U0 provide, and what is their voltage tolerance?

The M38B79FFFP#U0 provides exactly 52 high-breakdown-voltage P-channel open-drain output pins across ports P0–P5 and P60–P63. These pins tolerate up to 25 V (absolute maximum) when sinking current, enabling direct drive of fluorescent display segments without external high-voltage transistors.

Can the M38B79FFFP#U0 operate from a 3.3 V supply?

No - the M38B79FFFP#U0 Flash version requires VCC = 4.0–5.5 V per official specifications. While low-speed mode supports 2.7–5.5 V operation, the Flash programming voltage (VPP = 11.7–12.6 V) and internal regulator design mandate minimum 4.0 V for reliable Flash operation and I/O voltage levels. Use only 5 V ±10 % nominal supply.

What is the function of the VEE pin on the M38B79FFFP#U0, and how should it be biased?

The VEE pin supplies the pull-down reference voltage for high-breakdown-voltage output ports P0–P3. It must be externally biased to a voltage ≤ VSS (typically 0 V or slightly negative) to ensure proper turn-off of P-channel open-drain drivers. Leaving VEE floating or connecting it to VCC will prevent correct FLD segment control and may damage connected displays.