Renesas HD4074318S

Overview

HD4074318S from Renesas Electronics is a ZTAT™ PROM-based 4-bit HMCS400-series microcontroller with 8-kword on-chip PROM, integrated 8-bit × 8-channel A/D converter, three timers (event counter, timer output, input capture), and 34 I/O pins - 21 of which support 40 V high-voltage drive for direct fluorescent display interfacing. It operates at 1 µs instruction cycle time (f_osc = 4 MHz) and supports ceramic/crystal or external clock sources.

For engineers reviewing the HD4074318S datasheet, HD4074318S pinout, HD4074318S application, or HD4074318S equivalent, this page delivers verified technical context, MCU-mode and PROM-mode pin mapping, memory architecture details, interrupt priority structure, low-power mode behavior, and validated alternative options for legacy system maintenance and replacement design.

Technical Context

The HD4074318S implements a Harvard-architecture 4-bit CPU core with 101-instruction set, 14-bit program counter, and 10-bit stack pointer. Its memory map includes 8,192 × 10-bit PROM (program area $0000–$1FFF), 384 × 4-bit RAM, and dedicated register-mapped peripherals including A/D control registers (AMR1/AMR2, ADRL/ADRU), timer mode registers (TMA/TMB1/TMC), and serial interface registers (SMR, SRL/SRU).

It supports dual operational modes: MCU mode for normal execution with full peripheral operation, and PROM mode for in-circuit programming - where pins reconfigure as address/data/control lines (A0–A14, O0–O7, CE, OE) compatible with standard 27256 PROM programmers. Reset, STOPC, and TEST pins govern mode transitions and debug access.

Key Specifications

Pinout & Package

HD4074318S is packaged in DP-42S (42-pin plastic DIP) with 0.6-inch body width and 0.1-inch pin pitch. Pin functions differ between MCU mode (normal operation) and PROM mode (programming); both configurations are fully documented in the datasheet.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-bit microcontroller applications.

Compared with HD404318S, the HD4074318S offers field-programmable firmware without mask costs, while HD4074318H provides identical functionality in a surface-mount package - enabling migration from through-hole to modern assembly processes without firmware redesign.

Availability

HD4074318S is available at Aetrix Electronics and suitable for industrial panel meters, legacy appliance controllers, fluorescent display terminals, and test & measurement equipment requiring stable component supply and long-term obsolescence management.

Supply support for HD4074318S 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 Electronics Corporation is a Japanese semiconductor manufacturer formed in 2010 through the merger of NEC Electronics and Renesas Technology, specializing in microcontrollers, analog, and power devices for industrial and consumer applications.

The HD4074318S belongs to the HMCS400-series microcontroller family, designed specifically for cost-sensitive, low-power embedded control applications requiring integrated A/D, high-voltage I/O, and display driving capability - particularly in legacy industrial and home appliance systems.

FAQ

What is the PROM programming voltage required for HD4074318S?

The HD4074318S requires V_PP = +25 V applied to the TEST pin (Pin 6, DP-42S) during PROM programming mode. This high-voltage signal enables the internal PROM write circuitry. Programming must be performed using a compatible 27256-format PROM writer with appropriate socket adapter (e.g., Hitachi HS4318ESS01H for DP-42S). The HD4074318S datasheet specifies exact timing and voltage tolerances for reliable programming.

Does HD4074318S support crystal oscillator operation?

Yes, HD4074318S supports crystal oscillator operation via OSC1 (Pin 8) and OSC2 (Pin 9). A parallel-resonant quartz crystal (typically 4 MHz) can be connected directly across these pins with recommended load capacitors (15–30 pF each to ground). The internal oscillator circuit provides stable clock generation without external components, and the HD4074318S also accepts external clock signals applied to OSC1.

How many interrupt sources does HD4074318S have, and what are their priorities?

The HD4074318S has seven interrupt sources: two external (INT0, INT1), three timer-based (Timer A, Timer B, Timer C), one A/D conversion complete, and one serial interface. Priority order is fixed: RESET/STOPC (highest), INT0, INT1, Timer A, Timer B, Timer C, A/D, Serial (lowest). Vector addresses ($0000–$000E) are pre-assigned per priority level and cannot be remapped in hardware.

Can HD4074318S operate in low-power modes while retaining RAM contents?

Yes, HD4074318S supports Standby mode where the system oscillator continues running, CPU halts, and RAM contents are retained. In Stop mode, the oscillator stops, CPU resets, and RAM is retained but all peripherals (timers, A/D, serial) reset to initial state. Both modes reduce power consumption significantly compared to Active mode, and wake-up is triggered by RESET, STOPC, or external interrupts depending on configuration.

What is the maximum operating frequency of HD4074318S?

The HD4074318S has a maximum oscillator frequency of 4 MHz, resulting in a 1 µs instruction cycle time. This timing is specified under V_CC = 5 V ± 10% and operating temperature range of 0°C to +70°C. Operation above 4 MHz is not guaranteed and may cause timing violations in internal peripherals including the A/D converter and serial interface.