ATMEGA161L-4PI - 8-bit AVR MCU 4MHz 16KB Flash | Microchip
MPN: ATMEGA161L-4PI β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.93 | $8.93 |
| 10 | $8.22 | $82.20 |
| 100 | $7.45 | $745.00 |
| 500 | $6.9 | $3,450.00 |
| 1,000 | $6.35 | $6,350.00 |
ATMEGA161L-4PI Overview
A microcontroller (MCU) integrates a processor core, memory, and peripherals on a single chip, sitting at the device level of the embedded-systems hierarchy: microcontroller -> embedded processor -> integrated circuit. The AVR ATmega family is famous for its advanced RISC architecture with mostly single-cycle instruction execution, which yields high code density and deterministic timing compared to CISC 8-bit predecessors.
Key features of the ATMEGA161L-4PI include 130 powerful instructions with most executing in a single clock cycle, dual UART serial interfaces for multi-channel communication, an external oscillator design, and the L-suffix low-voltage operating window of 2.7V to 5.5V. The P suffix denotes industrial temperature operation, and the I suffix confirms the -40C to +85C industrial grade range, making the part suitable for uncontrolled environments.
Architecturally, the AVR core uses a Harvard structure with separate program and data buses, allowing simultaneous instruction fetch and data access. The 16KB Flash is in-system programmable, and the 512B EEPROM retains calibration or configuration data without external NVM. Peripherals include timers, the dual UARTs, and an SPI-style serial interface on port B.
Typical applications include legacy industrial control equipment, point-of-sale terminals, instrumentation front ends, motor control panels, and hobbyist or educational platforms that require through-hole DIP mounting for easy prototyping and socketed replacement.
Designers should note the 4MHz maximum clock rating of the L-grade device: do not clock it above 4MHz even if a faster ATMEGA161-16 variant tolerates it, and use an external crystal or oscillator as the device has no internal RC oscillator.
This page synthesizes distributor pricing, drop-in alternatives within the ATmega family, and practical migration guidance not found in the manufacturer datasheet.
Drop-in alternatives for ATMEGA161L-4PI β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ATMEGA161L-4PI (same form factor and footprint) β differing in Instruction Set, Package, Mounting Type, Operating Temperature, Flash Program Memory.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA161L-4PU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA161-16PI
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA16-16PI
β Drop-Inβ In Stock
$3.72 / Unit
View Datasheet βATMEGA16-16PC
β Drop-Inβ In Stock
$4.48 / Unit
View Datasheet βATMEGA16-16AU
β Drop-Inβ In Stock
$4.41 / Unit
View Datasheet βATMEGA161L-4PI Maximum Ratings & Electrical Characteristics
| Core Architecture | 8-bit AVR RISC |
| Core Series | AVR ATmega (ATmega161) |
| Maximum Clock Frequency | 4 MHz |
| Program Memory Size | 16 KB (8K x 16) Flash |
| SRAM Size | 1 KB (1K x 8) |
| EEPROM Size | 512 B |
| Supply Voltage Range | 2.7 V to 5.5 V |
| Number of I/O | 35 |
| Oscillator Type | External |
| Package / Case | 40-PDIP (0.600 in, 15.24 mm) |
| Operating Temperature | -40C to +85C (industrial) |
| Instruction Set | 130 instructions, most single-cycle |
| Packaging | Tray |
| Mounting Type | Through Hole |
| RoHS Status | ROHS (per LCSC listing) |
| Program Memory Type | FLASH |
| Interfaces | Dual UART, SPI (port B) |
ATMEGA161L-4PI 40-pdip (0.600 in, 15.24 mm) Pin Configuration Guide
Pin configuration for ATMEGA161L-4PI (40-pdip (0.600 in, 15.24 mm) package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for ATMEGA161L-4PI.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA161L-4PI is suitable for 6 applications: Legacy Industrial Control Systems, Dual-UART Protocol Converters, Point-of-Sale and Barcode Terminals, Instrumentation Front Ends, Educational and Hobbyist Platforms, Motor Control and Relay Panels.
Legacy Industrial Control Systems
The ATMEGA161L-4PI fits industrial control retrofits where an existing 40-DIP socket, validated firmware, and -40C to +85C operation must be preserved. Its industrial temperature rating and 2.7V-5.5V supply tolerance absorb unregulated cabinet supplies and cold-warehouse conditions, while the 16KB Flash and 1KB SRAM run ladder-logic-style control code in C or assembly at 4MHz. Because the part is through-hole, field technicians can replace a failed controller board chip in minutes without SMT rework. Maintain at least 0.1uF decoupling at pins 9/10 and keep the external crystal traces short to preserve noise immunity in motor-drive environments.
Recommended
Dual-UART Protocol Converters
The ATmega161 is unusual among 8-bit AVRs in offering two independent hardware UARTs, making the ATMEGA161L-4PI a natural fit for protocol converters, RS-485-to-RS-232 bridges, and multi-drop sensor concentrators. One UART can service a field bus at 9600 baud while the second streams diagnostics to a service port, with hardware buffering handled by the 1KB SRAM in software FIFOs. At 4MHz the core sustains aggregate serial throughput of roughly 38.4 kbaud per channel with interrupt service overhead to spare. Designs that need higher throughput should migrate to the pin-compatible ATMEGA16-16PI and multiplex its single UART or add an external DUART.
Recommended
Point-of-Sale and Barcode Terminals
Older POS terminals and barcode scanners were designed around the ATmega161's combination of Flash program memory for application updates, EEPROM for configuration persistence, and DIP packaging for serviceable main boards. The 35 I/O lines drive keypads, segment displays, and stepper-driven paper feeds, while the UART connects to receipt printers. The 2.7V-5.5V range tolerates battery-backed power sag during outages. When servicing these terminals, verify that replacement L-grade parts are used with the original 4MHz crystal - fitting a 16MHz-rated non-L part is acceptable electrically, but firmware written against ATmega161 registers must not be replaced with ATmega16 binaries without recompilation.
Recommended
Instrumentation Front Ends
Bench and panel instruments benefit from the ATMEGA161L-4PI's deterministic single-cycle instruction timing, which gives predictable scan rates for measurement sequencing without RTOS jitter. The 512B EEPROM stores calibration constants across power cycles, and the external oscillator allows a precision crystal locked to the instrument's timebase, ensuring baud and timing accuracy that internal-RC MCUs cannot match. The 4MHz rating keeps radiated emissions low for EMC-sensitive lab equipment. Note that the ATmega161 has no on-chip ADC, so external ADCs on the port B serial interface or parallel port A are required for analog inputs.
Recommended
Educational and Hobbyist Platforms
The 40-pin PDIP package and socket compatibility make the ATMEGA161L-4PI popular in education and retro-hobby projects: it plugs into breadboards and low-cost ZIF programmers, and the through-hole pins tolerate repeated insertion. Students can observe the Harvard AVR architecture, dual-UART operation, and ISP Flash programming at a forgiving 4MHz clock with a plain crystal. The 2.7V minimum supply allows safe 3.3V logic experiments alongside 5V peripherals. Educators should note the part's EOL status when planning curricula and standardize on the actively produced ATMEGA16-16PI for new lab stock, since register mappings are broadly similar across both ATmega generations.
Recommended
Motor Control and Relay Panels
In pump, gate, and relay control panels, the ATMEGA161L-4PI's industrial temperature grade and wide supply window provide dependable sequencing logic, with port C and port D driving opto-isolated triac or relay channels through ULN-series drivers. The timer peripherals generate PWM or time-delay sequences, and the UART logs fault events to a supervisory controller. Through-hole construction withstands vibration better than fine-pitch SMT in harsh cabinets, and field replacement is trivial. Keep inductive-load switching physically separated from the crystal and decoupling network, and clamp transients at the I/O pins to protect the 35 general-purpose lines.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA161L-4PI β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA161L-4PU | ATMEGA161-16PI | ATMEGA16-16PI | ATMEGA16-16AU |
|---|---|---|---|---|---|
| Package | 40-PDIP (0.600 in) | 40-PDIP - same | 40-PDIP - same | 40-PDIP - same | 44-TQFP - different footprint |
| Brand | Microchip Technology (Atmel) | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Max Clock Frequency | 4 MHz | 4 MHz | 16 MHz | 16 MHz | 16 MHz |
| Flash Program Memory | 16 KB | 16 KB | 16 KB | 16 KB | 16 KB |
| SRAM / EEPROM | 1 KB / 512 B | 1 KB / 512 B | 1 KB / 512 B | 1 KB / 512 B | 1 KB / 512 B |
| Supply Voltage | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Operating Temperature | -40C to +85C (industrial) | 0C to +70C (commercial) | -40C to +85C (industrial) | -40C to +85C (industrial) | -40C to +85C (industrial) |
| Distinct Feature | Dual hardware UART, no ADC | Dual UART, no ADC | Dual UART, no ADC | Single UART, 10-bit ADC, internal RC osc | Single UART, 10-bit ADC, internal RC osc |
| Lifecycle Status | EOL (aftermarket via Rochester) | EOL | EOL | Active | Active |
Key Differentiators
- True dual hardware UART (vs ATMEGA16-16PI)
- Low-voltage 2.7V operation at 4MHz (vs ATMEGA161-16PI)
- External oscillator for precision timing (vs ATMEGA16-16PI)
- Honest trade-off: end-of-life supply risk (vs ATMEGA161L-4PU)
Design Notes
Respect the 4MHz ceiling of the L-grade device. The ATMEGA161L-4PI is qualified to 4MHz over its 2.7V-5.5V range; fitting a 16MHz crystal (valid for ATMEGA161-16 parts) will violate its timing specification and cause erratic UART baud rates and unstable execution. Always verify the suffix on incoming stock - the 4/16 speed code and the L suffix are the two characters most often mixed up in legacy kitting.
The ATmega161 has no internal RC oscillator, so the external crystal circuit is the system clock - a failure here halts the MCU. Place the crystal and two load capacitors within 10mm of the XTAL pins, guard them with a ground ring, and add 0.1uF ceramic decoupling directly across the VCC/GND pair (DIP pins 9/10 region). For 3.3V operation, confirm crystal drive level is not exceeded at low voltage; the ATmega161 datasheet application section provides the recommended oscillator network values.
When migrating to the pin-compatible ATMEGA16-16PI, budget firmware rework: the ATmega161's dual UART maps to a single UART with different register addresses, interrupt vectors are renumbered, and the ATMEGA16 adds an ADC and internal oscillator whose fuses default differently. Recompile, verify UART timing on a scope, and check fuse settings (especially clock source and Brown-out) before first power-up on converted boards.
Compliance Information
LCSC listing marks the ATMEGA161L-4PI as ROHS. REACH, halogen-free, and conflict-minerals status not stated in the provided data.
