Silicon Labs C8051F321R

Overview

C8051F321R from Silicon Laboratories is a fully integrated 8051-based microcontroller with on-chip Full Speed USB 2.0 controller, 16 kB ISP flash, 2304 B RAM, 10-bit 200 ksps ADC, and precision internal oscillator (0.25% accuracy with clock recovery). It operates from 4.0–5.25 V and supports -40°C to +85°C industrial temperature range in a 28-pin MLP package.

For engineers reviewing the C8051F321R datasheet, C8051F321R pinout, C8051F321R application, or C8051F321R equivalent, key selection considerations include USB clock recovery without external crystal, 5 V-tolerant I/O, on-chip debug via C2 interface, and real-time clock capability using PCA or timer with external clock source.

Technical Context

The C8051F321R implements a pipelined CIP-51 core delivering up to 25 MIPS at 25 MHz, with expanded interrupt handling (16 sources) and memory-mapped peripherals accessed via priority crossbar. Its USB subsystem complies with USB 2.0, supports eight flexible endpoints, and integrates transceiver and 1 kB buffer - eliminating external resistors and crystal for full-speed operation.

Analog functionality includes a 10-bit ADC with up to 17 single-ended or 13 differential inputs, programmable VREF source (external, internal, or VDD), built-in temperature sensor, and two comparators with reset capability. Digital peripherals comprise hardware-enhanced SPI, SMBus, UART, four 16-bit timers, and a 16-bit PCA with five capture/compare modules.

Key Specifications

Pinout & Package

28-pin MLP (5 × 5 mm, 0.5 mm pitch) package with exposed thermal pad; designed for compact USB-enabled embedded applications requiring minimal board area and no external crystal.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar USB-enabled 8051 microcontroller applications.

Compared with C8051F321R, C8051F340 offers greater memory and I/O scalability but lacks integrated USB clock recovery, while CP2102N-A02-GM provides lower-cost serial bridging without programmability or analog capability - making C8051F321R optimal for compact, self-contained USB MCU applications requiring mixed-signal integration.

Availability

C8051F321R is available at Aetrix Electronics and suitable for USB HID devices, industrial sensor nodes, PLC I/O modules, and firmware upgrade adapters requiring stable component supply and long-term industrial availability.

Supply support for C8051F321R 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

Silicon Laboratories is a fabless semiconductor company specializing in mixed-signal ICs for timing, wireless, MCU, and sensor applications, with emphasis on integration and system-level optimization.

The C8051F32x family was designed to deliver USB-enabled 8051 performance in minimal footprint, targeting cost-sensitive, space-constrained embedded systems requiring native USB connectivity and analog sensing.

FAQ

Does the C8051F321R require an external crystal for USB operation?

No, the C8051F321R integrates a USB clock recovery circuit that enables Full Speed (12 Mbps) and Low Speed (1.5 Mbps) USB operation without any external crystal or oscillator. This eliminates BOM cost and layout complexity associated with external timing components while maintaining USB specification compliance. The internal oscillator achieves 0.25% accuracy when clock recovery is enabled, ensuring reliable USB communication for the C8051F321R.

What is the maximum sampling rate of the ADC in the C8051F321R?

The C8051F321R features a 10-bit successive-approximation ADC (ADC0) with a maximum throughput of 200 ksps (kilo-samples per second) under optimal conditions - including appropriate VREF stability, input settling time, and conversion mode configuration. This rate applies to single-ended conversions with internal reference and minimal channel switching; actual sustained rate depends on system clock, analog input impedance, and software overhead in the C8051F321R application.

How many I/O pins does the C8051F321R provide, and are they 5 V tolerant?

The C8051F321R provides 21 general-purpose I/O pins (P0.0–P0.7, P1.0–P1.7, P2.0–P2.4, plus P3.0/P3.1 shared with USB) - all configured as 5 V tolerant with high sink current capability. This allows direct interfacing with standard 5 V logic families without external level shifters, simplifying design in mixed-voltage systems and enhancing robustness in industrial environments where the C8051F321R is commonly deployed.

Can the C8051F321R be debugged in-system without an emulator?

Yes, the C8051F321R includes on-chip debug circuitry accessible via the 2-wire C2 interface (C2CK and C2D pins), enabling full-speed, non-intrusive in-system debugging. Engineers can set breakpoints, single-step code, and inspect/modify registers and memory directly on the target hardware - eliminating the need for ICE chips, target pods, or sockets. This capability is fully supported in Simplicity Studio for the C8051F321R.

What packaging options are available for the C8051F321R?

The C8051F321R is exclusively offered in a 28-pin MLP (Micro Lead Frame Package) with 5 × 5 mm body size and 0.5 mm pin pitch, featuring an exposed thermal pad for enhanced power dissipation. This compact, near-chip-scale package supports fine-pitch surface-mount assembly and is optimized for space-constrained USB peripheral designs where the C8051F321R delivers integrated functionality without external components.