Microchip Technology ATSTK503

Overview

ATSTK503 from Atmel (now Microchip Technology) is a top-module evaluation board designed to extend the STK500 development system for 100-pin AVR microcontrollers including ATmega2560, ATmega1280, and ATmega640. It features a Zero Insertion Force (ZIF) socket for TQFP packages, on-board 32 kHz crystal for RTC, RS-232 transceiver supporting 1.8–5.5 V operation, and full-port access (E, F, G, H, J, K, L) with VCC/GND per connector.

For engineers reviewing the ATSTK503 datasheet, ATSTK503 pinout, ATSTK503 application, or ATSTK503 equivalent, key selection considerations include ZIF socket compatibility with 100-pin TQFP AVRs, support for ISP/HVPP/JTAG programming modes via STK500, external memory interface capability with SRAM footprint and address latch, and flexible clock source switching between STK500-generated signal and on-board crystals.

Technical Context

The ATSTK503 operates exclusively as a hardware extension module-not a standalone board-and requires mechanical and electrical integration with the STK500 base unit via EXPAND0/EXPAND1 headers. It provides direct access to all I/O ports of supported AVRs through labeled 10-pin connectors, each delivering port pins plus dedicated VCC and GND.

Its external memory interface implements the AVR's multiplexed bus architecture: PORTA carries AD[7:0], PORTC supplies A[15:8], and PORTG[2:0] delivers RD, WR, and ALE signals. An on-board 74HC373 latch captures PORTA's address/data low byte on ALE assertion, enabling connection to 128K×8 SOJ/TSOP SRAM devices with center-power-pin configuration.

Key Specifications

Availability

ATSTK503 is available at Aetrix Electronics and suitable for embedded prototyping, AVR firmware validation, and educational MCU labs requiring stable component supply and legacy toolchain compatibility with AVR Studio 4.

Supply support for ATSTK503 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 (formerly Atmel Corporation) is a U.S.-based semiconductor company specializing in microcontrollers, analog components, and development tools for embedded systems.

The ATSTK503 belongs to Atmel's STK500 ecosystem and was engineered to accelerate evaluation and firmware development for high-pin-count AVR MCUs with integrated peripherals, external memory support, and multi-mode debugging capabilities.

FAQ

What is the primary function of the ATSTK503 in the STK500 development system?

The ATSTK503 serves as a top-module expansion card that enables the STK500 base unit to support 100-pin TQFP-packaged AVR microcontrollers-specifically ATmega2560, ATmega1280, and ATmega640. It adds critical hardware including a ZIF socket, full-port connectors, RS-232 transceiver, external memory interface, and dual-clock switching. The ATSTK503 does not operate independently and must be mounted on STK500 using aligned EXPAND0/EXPAND1 headers to establish power, signal, and programming connectivity.

Which AVR microcontrollers are officially supported by the ATSTK503?

The ATSTK503 is explicitly validated for use with three 100-pin TQFP AVR microcontrollers: ATmega2560, ATmega1280, and ATmega640. These devices share compatible pinouts, memory mapping, and peripheral sets required for the board's port routing, memory interface, and programming logic. The ATSTK503 documentation explicitly excludes AVRs with integrated LCD controllers (e.g., ATmega3290/ATmega6490), which require the STK504 instead.

Does the ATSTK503 include an on-board crystal oscillator, and how is it used?

Yes, the ATSTK503 includes two crystal-related resources: a 32 kHz crystal dedicated to the TOSC input for asynchronous timer/RTC applications, and a socket for user-supplied crystals (recommended for >8 MHz operation). The TOSC switch selects between connecting this 32 kHz crystal or routing PORTG pins to the TOSC inputs. The XTAL switch selects between STK500's programmable oscillator (≤3.69 MHz) or the STK503 crystal socket for the main XTAL input used by the AVR's system clock.

Can the ATSTK503 be used without the STK500 base board?

No, the ATSTK503 cannot function independently. It lacks onboard power regulation, USB/serial interface, programming voltage generation, or master control logic. All power, programming signals (ISP/HVPP/JTAG), clock distribution, and RS-232 control depend entirely on the STK500 base unit. Mounting requires precise alignment of EXPAND0 and EXPAND1 headers, and operation assumes STK500 firmware and AVR Studio 4 integration-making the ATSTK503 strictly a dependent top-module within the STK500 ecosystem.

What types of SRAM devices are compatible with the ATSTK503 footprint?

The ATSTK503 supports 128K×8-bit SRAM chips in SOJ (300-mil or 400-mil) and TSOP-II packages with center power pin configuration (VCC centered between ground pins). Validated parts include ISSI IS63LV1024 series, IDT IDT71V124SA variants, Cypress CY7C1019B-V/CY7C1018BV33-V, Toshiba TC55V8128BFT, Samsung K6R1008C1C-T, and Alliance AS7C31025A-HFC. The board's RAM HIGH ADDRESS jumpers allow disabling A[15:8] to repurpose those lines as general-purpose I/O when smaller memory maps are used.