Microchip Technology ATSTK501

Overview

ATSTK501 from Microchip Technology (formerly Atmel) is a top-module evaluation board designed to extend the STK500 development system with full hardware support for ATmega103(L) and ATmega128(L) microcontrollers. It provides a ZIF socket for TQFP packages, JTAG debugging interface, dual-port RS-232C with RTS/CTS, external 128KB SRAM footprint, and dedicated PORT E/F/G/AUX I/O headers - enabling rapid prototyping of memory-intensive AVR applications including industrial control and embedded communications.

For engineers reviewing the ATSTK501 datasheet, ATSTK501 pinout, ATSTK501 application, or ATSTK501 equivalent, this page delivers verified technical context on SRAM address expansion (A16), software-controllable SRAMEN enable logic, TOSC switch configuration for 32 kHz RTC crystal routing, JTAG ICE compatibility, and jumper-based RAM high-address byte management - all critical for XRAM-enabled firmware development and hardware bring-up.

Technical Context

The ATSTK501 interfaces directly with the STK500 base board via EXPAND0/EXPAND1 headers and supports both in-system programming (ISP) and high-voltage parallel programming for ATmega103(L)/128(L). Its SRAM subsystem uses a 74AHC573 latch to drive A[7:0], with A16 routed separately and SRAMEN controlling chip-enable polarity (active-low).

Port expansion includes full PORT E (8-bit), PORT F (8-bit), and PORT G (5-bit + AUX signals: A16, SRAMEN, PEN), while the TOSC switch selectively routes PG3/PG4 between 32 kHz crystal or GPIO function. The RS-232C port implements logic-level translation via MAX3232ECAE and supports hardware flow control lines (RTS/CTS) for UART-based communication testing.

Key Specifications

Availability

ATSTK501 is available at Aetrix Electronics and suitable for AVR microcontroller development, embedded firmware validation, and industrial control prototyping requiring stable component supply and legacy toolchain continuity.

Supply support for ATSTK501 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

Microchip Technology acquired Atmel Corporation in 2016 and maintains full legacy support for AVR development tools. Atmel originally designed and qualified the STK501 for robustness in engineering labs and university teaching environments.

The ATSTK501 belongs to the STK500 ecosystem - a modular, expandable platform built to accelerate AVR MCU evaluation, debug, and production-ready firmware development across automotive, industrial, and consumer applications.

FAQ

What is the primary function of the ATSTK501 in the STK500 development system?

The ATSTK501 serves as a top-module expansion board that adds native hardware support for ATmega103(L) and ATmega128(L) microcontrollers to the STK500 base unit. It provides essential interfaces including ZIF socket for TQFP packages, JTAG debugging, external SRAM footprint, and extended I/O ports (PORT E/F/G), enabling full utilization of advanced features like XRAM and dual UARTs during firmware development and validation of ATSTK501-based designs.

Does the ATSTK501 require a separate power supply or is it powered by the STK500?

The ATSTK501 draws all operating power from the STK500 base board via the EXPAND0 and EXPAND1 headers - no external power supply is needed. It operates within the STK500's regulated VTG (target voltage) and AVTG (analog voltage) rails, supporting 2.7V–5.5V input range as specified in the ATSTK501 technical documentation.

How is external SRAM enabled and configured on the ATSTK501?

External SRAM is enabled on the ATSTK501 by connecting the SRAMEN pin (on PORTG/AUX header) to GND using a supplied jumper - asserting active-low chip-enable. The A16 signal controls upper memory bank selection, and RAM high-address jumpers configure Port C pins for address vs. general-purpose I/O. The ATSTK501 supports up to 128KB SRAM, with software-managed A16 toggling required to access beyond the default 64KB boundary.

Can the ATSTK501 be used with microcontrollers other than ATmega103(L) and ATmega128(L)?

Yes - the ATSTK501's SRAM interface and PORT headers can be adapted for AT90S8515 and ATmega161(L) using manual signal strapping (WR→PG0, RD→PG1, ALE→PG2) as documented in Section 2.8 of the ATSTK501 User Guide. However, JTAG debugging and PORT G functionality are exclusive to ATmega128(L), and ATmega103(L) lacks PORT G entirely - confirming ATSTK501's core compatibility remains focused on those two devices.

What is the role of the TOSC switch on the ATSTK501?

The TOSC switch on the ATSTK501 selects routing between the onboard 32 kHz crystal and PORT G pins PG3/TOSC2 and PG4/TOSC1. When engaged, the crystal connects directly to the ATmega128(L)'s oscillator inputs for real-time clock (RTC) applications; when disengaged, PG3 and PG4 become general-purpose I/O. This switch ensures flexible timing resource allocation without hardware modification - a key design feature confirmed in Section 2.9 of the ATSTK501 User Guide.