atmega32u4-16mu ATMEL Corporation, atmega32u4-16mu Datasheet - Page 332

• Manufacturer Part Number: atmega32u4-16mu
• Description: Atmega32u4 8-bit Avr Microcontroller With 32k Bytes Of Isp Flash And Usb Controller
• Manufacturer: ATMEL Corporation

26. JTAG Interface and On-chip Debug System
26.0.1
26.1
26.2
332
Overview
Test Access Port – TAP
ATmega32U4
Features
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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 384
339
and distributed within ATMEL and to selected third party vendors only.
Figure 26-1
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:
• 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
• TCK: Test Clock. JTAG operation is synchronous to TCK.
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
machine.
, respectively. The On-chip Debug support is considered being private JTAG instructions,
– 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
shows a block diagram of the JTAG interface and the On-chip Debug system. The
and
®
“IEEE 1149.1 (JTAG) Boundary-scan” on page
7766A–AVR–03/08
“Program-