atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 217

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

24. JTAG Interface and On-chip Debug System
24.1
24.2
24.3
2570L–AVR–08/07
Features
Overview
TAP – Test Access Port
•
•
•
•
•
•
The AVR IEEE std. 1149.1 compliant JTAG interface can be used for
•
•
•
A brief description is given in the following sections. Detailed descriptions for Programming via
the JTAG interface, and using the Boundary-scan Chain can be found in the sections
ming via the JTAG Interface” on page 283
223, respectively. The On-chip Debug support is considered being private JTAG instructions,
and distributed within ATMEL and to selected third party vendors only.
Figure 24-1
TAP Controller is a state machine controlled by the TCK and TMS signals. The TAP Controller
selects either the JTAG Instruction Register or one of several Data Registers as the scan chain
(Shift Register) between the TDI – input and TDO – output. The Instruction Register holds JTAG
instructions controlling the behavior of a Data Register.
The ID-Register, Bypass Register, and the Boundary-scan Chain are the Data Registers used
for board-level testing. The JTAG Programming Interface (actually consisting of several physical
and virtual Data Registers) is used for serial programming via the JTAG interface. The Internal
Scan Chain and Break Point Scan Chain are used for On-chip debugging only.
The JTAG interface is accessed through four of the AVR’s pins. In JTAG terminology, these pins
constitute the Test Access Port – TAP. These pins are:
•
•
•
JTAG (IEEE std. 1149.1 Compliant) Interface
Boundary-scan Capabilities According to the IEEE std. 1149.1 (JTAG) Standard
Debugger Access to:
Extensive On-chip Debug Support for Break Conditions, Including
Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface
On-chip Debugging Supported by AVR Studio
– All Internal Peripheral Units
– Internal and External RAM
– The Internal Register File
– Program Counter
– EEPROM and Flash Memories
– AVR Break Instruction
– Break on Change of Program Memory Flow
– Single Step Break
– Program Memory Break Points on Single Address or Address Range
– Data Memory Break Points on Single Address or Address Range
Testing PCBs by using the JTAG Boundary-scan capability
Programming the non-volatile memories, Fuses and Lock bits
On-chip debugging
TMS: Test mode select. This pin is used for navigating through the TAP-controller state
machine.
TCK: Test Clock. JTAG operation is synchronous to TCK.
TDI: Test Data In. Serial input data to be shifted in to the Instruction Register or Data
Register (Scan Chains).
shows a block diagram of the JTAG interface and the On-chip Debug system. The
and
ATmega325/3250/645/6450
®
“IEEE 1149.1 (JTAG) Boundary-scan” on page
“Program-
217