Microchip Technology ATSTK505

Overview

ATSTK505 from Microchip Technology (formerly Atmel) is a plug-in top module for the STK500 development system, designed to enable hardware evaluation and programming of 14-pin SOIC ATtiny24 and 20-pin PDIP ATtiny26 microcontrollers. It provides ZIF and DIP sockets, clock source selection switches, reset/I/O configuration, crystal sockets, and dual-mode programming interfaces (ISP and HV).

For engineers reviewing the ATSTK505 datasheet, ATSTK505 pinout, ATSTK505 application, or ATSTK505 equivalent, this page details its target-device support, socket compatibility, clock/reset switch logic, ISP/HV programming connectivity, and integration requirements with STK500 - all critical for AVR prototyping, fuse configuration, and production-ready firmware validation.

Technical Context

The ATSTK505 operates exclusively as an expansion board for the STK500 base unit and does not function independently. It implements two physically segregated target sections - green for ATtiny24 (14-pin SOIC via ZIF socket) and blue for ATtiny26 (20-pin PDIP via DIP socket) - with dedicated SPROG headers, clock selection switches (XTAL/EXT CLK/INT RC), and RESET/PORTB toggle switches per section.

Hardware-level signal routing is controlled by mechanical switches and jumpers: the XTAL switch routes XTAL1/XTAL2 to crystal sockets, external clock, or PORTB header; the RESET switch connects the reset pin to STK500's reset signal or PORTB header; both require correct fuse settings (e.g., RSTDISBL, SPIEN) in the target AVR to function as intended.

Key Specifications

Availability

ATSTK505 is available at Aetrix Electronics and suitable for AVR microcontroller evaluation, fuse configuration, low-volume firmware development, and educational labs requiring stable component supply and legacy Atmel toolchain compatibility.

Supply support for ATSTK505 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 legacy AVR development tools under its portfolio. The company specializes in microcontrollers, analog, interface, and memory solutions for embedded applications.

The ATSTK505 belongs to the STK500 ecosystem product line, engineered specifically to extend the STK500 base board's capability for early-stage AVR device bring-up, clock/fuse validation, and hardware-assisted debugging of ATtiny24 and ATtiny26 devices.

FAQ

What is the primary function of the ATSTK505 in the STK500 development system?

The ATSTK505 serves as a dedicated top-module expansion card for the STK500, enabling physical socketing, clock configuration, reset control, and programming of ATtiny24 and ATtiny26 microcontrollers. It does not operate standalone and requires full integration with STK500 for power, communication, and programming signals. Its design focuses on hardware-level flexibility for fuse setting, clock source validation, and I/O pin reassignment during early AVR development.

Which microcontrollers are supported by the ATSTK505, and how are they physically interfaced?

The ATSTK505 supports only the ATtiny24 in 14-pin SOIC package (via ZIF socket) and the ATtiny26 in 20-pin PDIP package (via DIP socket). Each device occupies a separate color-coded section - green for ATtiny24 and blue for ATtiny26 - with independent clock switches, reset switches, SPROG headers, and crystal sockets. No other AVR devices or packages are compatible.

How does the XTAL switch on the ATSTK505 affect signal routing for ATtiny24 and ATtiny26?

The XTAL switch on the ATSTK505 controls whether XTAL1 and XTAL2 pins connect to the on-board crystal socket (XTAL position), STK500's external clock source (EXT CLK position), or the PORTB header (INT RC position). This routing is hardware-level and requires matching fuse settings in the target AVR - for example, using the CKSEL bits to select crystal mode when the switch is in XTAL position.

What programming interfaces does the ATSTK505 provide, and what cables are required?

The ATSTK505 supports both In-System Programming (ISP) and High-Voltage Programming (HVP). ISP uses a 6-pin cable between STK500's ISP6PIN and the corresponding SPROG header (green for ATtiny24, blue for ATtiny26). HVP requires 10-pin cables: PROGDATA and PROGCTRL connections differ between ATtiny24 (serial HVP) and ATtiny26 (parallel HVP), with specific jumper settings on both STK500 and ATSTK505.

Why does the ATSTK505 include separate RESET/PORTB switches for each target section?

The RESET/PORTB switch allows the AVR's reset pin to be either driven by STK500's reset signal (RESET position) or exposed as a general-purpose I/O pin on the PORTB header (PORTB position). Using it as an I/O pin requires programming the RSTDISBL fuse in the target device - a one-time irreversible action unless a high-voltage programmer is available. The switch enables safe, reversible configuration during development and testing of reset-sensitive firmware.