JTAG stands for “Joint Test Action Group” which was standardized as the IEEE 1149.1 Standard Test Access Port and Boundary-Scan Architecture in 1990. JTAG [[wysiwyg_imageupload::]]is generally used in IC debugging and device programming. Atmega16 consists of one JTAG port which shares four pins with PORTC. Until JTAG port is not disabled, these pins can’t be used as normal I/O pins. This article explores the methods for JTAG disabling. JTAG interface shares PC2, PC3, PC4 and PC5 of ATmega16. To use these four pins for general I/O operations, JTAG must be disabled. There are two methods for disabling JTAG: 1. By programming2. Using AvrdudeThere is a register in atmega16 MCUCSR (MCU control and status register). It consists of JTD (JTAG disable) bit as 7th bit of register. JTAG can be disabled by writing 1 to this bit.JTAG can be permanently disabled by configuring two fuse bits, OCDEN and JTAGEN (must be disabled). This is done by using Avrdude software.