4.4
tinyAVR
®
, megaAVR
®
, and XMEGA
®
Devices
AVR devices feature various programming and debugging interfaces. Check the device data sheet for supported
interfaces of that device.
• 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
debugWIRE
JTAG
PDI
aWire
SWD
tinyAVR
New
devices
Some
devices
Some
devices
Some devices
megaAVR
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). Microchip 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
target
device
4.4.2
Connecting to a JTAG Target
The Power Debugger 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 Debug header. The
Power Debugger
On-chip Debugging
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2020 Microchip Technology Inc.
User Guide
DS40002201A-page 64