• Some tinyAVR
®
devices have a TPI interface. TPI can be used for programming the device only,
and these devices do not have on-chip debug capability at all.
• Some tinyAVR devices and some megaAVR devices have the debugWIRE interface, which
connects to an on-chip debug system known as tinyOCD. All devices with debugWIRE also have
the SPI interface for in-system programming.
• Some megaAVR devices have a JTAG interface for programming and debugging, with an on-chip
debug system also known as megaOCD. All devices with JTAG also feature the SPI interface as an
alternative interface for in-system programming.
• All AVR XMEGA devices have the PDI interface for programming and debugging. Some AVR
XMEGA devices also have a JTAG interface with identical functionality.
• New tinyAVR devices have a UPDI interface, which is used for programming and debugging
Table 4-9. Programming and Debugging Interfaces Summary
UPDI TPI SPI debugWIR
E
JTAG PDI aWire SWD
tinyAVR New
devices
Some
devices
Some
devices
Some
devices
megaAV
R
All
devices
Some
devices
Some
devices
AVR
XMEGA
Some
devices
All
devices
AVR UC All
devices
Some
devices
SAM Some
devices
All
devices
4.4.1. JTAG Physical Interface
The JTAG interface consists of a 4-wire Test Access Port (TAP) controller that is compliant with the IEEE
®
1149.1 standard. The IEEE standard was developed to provide an industry-standard way to efficiently test
circuit board connectivity (Boundary Scan). Atmel AVR and SAM devices have extended this functionality
to include full Programming and On-chip Debugging support.
Figure 4-9. JTAG Interface Basics
Vcc
TMS
TDI
TDO
TCK
programmer /
debugger
Atmel
target
device
4.4.2. Connecting to a JTAG Target
The Atmel-ICE is equipped with two 50-mil 10-pin JTAG connectors. Both connectors are directly
electrically connected, but conform to two different pinouts; the AVR JTAG header and the ARM Cortex
Atmel Atmel-ICE [USER GUIDE]
Atmel-42330C-Atmel-ICE_User Guide-10/2016
36
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