AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 282

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

JTAG Interface and On-chip Debug System
Features
Overview
Test Access Port – TAP
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AT90CAN128
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The AVR IEEE std. 1149.1 compliant JTAG interface can be used for:
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A brief description is given in the following sections. Detailed descriptions for Program-
ming via the JTAG interface, and using the Boundary-scan Chain can be found in the
sections “JTAG Programming Overview” on page 340 and “Boundary-scan IEEE 1149.1
(JTAG)” on page 288, respectively. The On-chip Debug support is considered being pri-
vate JTAG instructions, and distributed within ATMEL and to selected third party
vendors only.
Figure 138 shows a block diagram of the JTAG interface and the On-chip Debug sys-
tem. The 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 Reg-
isters 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 (IDentifier 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 pro-
gramming 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:
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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).
TDO: Test Data Out. Serial output data from Instruction Register or Data Register
(Scan Chains).
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4250C–CAN–03/04