STMicroelectronics ST72F321J9T6

Overview

ST72F321J9T6 from STMicroelectronics is a 44-pin LQFP 8-bit microcontroller featuring 60KB on-chip HDFlash, 2KB RAM, 10-bit ADC with up to 16 channels, five timers (including PWM auto-reload and dual 16-bit), and three serial interfaces (SPI, SCI, I²C). It operates from 3.8V to 5.5V across –40°C to +85°C and targets industrial control, motor management, and sensor interface applications requiring in-application programming and low-power operation.

For engineers reviewing the ST72F321J9T6 datasheet, ST72F321J9T6 pinout, ST72F321J9T6 application, or ST72F321J9T6 equivalent, this MCU delivers deterministic real-time response via nested interrupt handling (14 vectors), configurable watchdog, PLL-based clock multiplication, and hardware-accelerated 8×8 unsigned multiply - critical for embedded firmware with timing-critical peripherals and memory-constrained code space.

Technical Context

The ST72F321J9T6 implements the ST7 core with 63 basic instructions and 17 addressing modes, supporting in-circuit and in-application programming of its 60KB HDFlash memory (100 write/erase cycles, 40-year data retention at 85°C). Its clock system integrates crystal/resonator oscillators, internal RC, external clock bypass, and a 2× PLL for flexible frequency scaling.

Interrupt management includes top-level interrupt (TLI) support, 15 external interrupt lines mapped across four vectors, and priority-based nested servicing. Power management provides four low-power modes (Halt, Active-Halt, Wait, Slow), each with distinct peripheral enable/disable states and wake-up source configurations.

Key Specifications

Pinout & Package

LQFP44 (10 × 10 mm, 0.8 mm pitch) package with 44 leads; thermally enhanced for sustained operation in enclosed industrial enclosures.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STM8S207R8T6 and EFM8BB52F64G-B-QFP48, the ST72F321J9T6 offers unique value in legacy-compatible ST7 firmware ecosystems, integrated beeper/RTC, and proven reliability in industrial temperature ranges - making it optimal for cost-sensitive, long-lifecycle replacements where minimal redesign is required.

Availability

ST72F321J9T6 is available at Aetrix Electronics and suitable for industrial motor control, smart sensor nodes, PLC I/O modules, and appliance control panels requiring stable component supply and long-term production continuity.

Supply support for ST72F321J9T6 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power devices, sensors, and analog ICs for industrial, automotive, and consumer markets.

The ST7 family was engineered for cost-effective, high-reliability 8-bit control in harsh environments - emphasizing flash endurance, wide temperature operation, and integrated peripherals to reduce system-level BOM count.

FAQ

Does ST72F321J9T6 support in-circuit debugging?

Yes, the ST72F321J9T6 supports in-circuit debugging via the single-wire ST-LINK interface using the STVP (ST Visual Programmer) and STVD (ST Visual Develop) tools. It includes hardware breakpoints, watchpoints, and real-time variable inspection without requiring dedicated debug pins - all functionality is accessible through the standard SWIM (Single-Wire Interface Module) pin.

What is the maximum ADC sampling rate achievable?

The ST72F321J9T6 ADC achieves a maximum conversion rate of 100 kSPS under typical conditions (VDD = 5V, f_ADC = 4 MHz). Conversion time is 13 ADC clock cycles per sample, and the ADC clock is derived from the system clock divided by a programmable prescaler - enabling trade-offs between resolution stability and throughput.

Can the PLL be disabled after startup to reduce power consumption?

Yes, the PLL can be disabled dynamically via the CLK_CR register's PLLEN bit. When disabled, the system clock reverts to the selected base oscillator (e.g., internal RC or crystal). This is commonly used in low-power modes like Wait or Slow to cut dynamic power by >40%, while retaining the ability to re-enable PLL for burst-mode processing.

Is there hardware support for I²C clock stretching?

Yes, the ST72F321J9T6's I²C peripheral includes automatic clock stretching support: when the CPU is unable to service an I²C interrupt within the SCL low period, the hardware holds SCL low until the ISR completes. This prevents data loss during high-priority foreground tasks and ensures compliance with I²C specification timing constraints.