...........continued
Power Debugger AVR PORT Pin
Target Pins
Mini-Squid Pin
Microchip STK600 PDI Pinout
Pin 10 (GND)
0
4.4.7
UPDI Physical Interface
The Unified Program and Debug Interface (UPDI) is a Microchip proprietary interface for external programming and
on-chip debugging of a device. It is a successor to the PDI 2-wire physical interface, which is found on all AVR
XMEGA devices. UPDI is a single-wire interface providing a bidirectional half-duplex asynchronous communication
with the target device for purposes of programming and debugging.
When designing an application PCB, which includes an Microchip AVR with the UPDI interface, the pinout shown
below should be used. One of the 6-pin adapters provided with the Power Debugger kit can then be used to connect
the Power Debugger probe to the application PCB.
Figure 4-12. UPDI Header Pinout
4.4.7.1
UPDI and /RESET
The UPDI one-wire interface can be a dedicated pin or a shared pin, depending on the target AVR device. Consult
the device data sheet for further information.
When the UPDI interface is on a shared pin, the pin can be configured to be either UPDI, /RESET, or GPIO by setting
the RSTPINCFG[1:0] fuses.
The RSTPINCFG[1:0] fuses have the following configurations, as described in the data sheet. The practical
implications of each choice are given here.
Table 4-13. RSTPINCFG[1:0] Fuse Configuration
RSTPINCFG[1:0] Configuration
Usage
00
GPIO
General purpose I/O pin. In order to access UPDI, a 12V pulse must be applied
to this pin. No external Reset source is available.
01
UPDI
Dedicated programming and debugging pin. No external Reset source is
available.
10
Reset
Reset signal input. In order to access UPDI, a 12V pulse must be applied to this
pin.
11
Reserved
NA
Note:
Older AVR devices have a programming interface, known as “High-Voltage Programming” (both serial and
parallel variants exist.) In general, this interface requires 12V to be applied to the /RESET pin for the duration of the
programming session. The UPDI interface is an entirely different interface. The UPDI pin is primarily a programming
and debugging pin, which can be fused to have an alternative function (/RESET or GPIO). If the alternative function is
selected then a 12V pulse is required on that pin in order to re-activate the UPDI functionality.
Note:
If a design requires the sharing of the UPDI signal due to pin constraints, steps must be taken in order to
ensure that the device can be programmed. To ensure that the UPDI signal can function correctly, as well as to avoid
damage to external components from the 12V pulse, it is recommended to disconnect any components on this pin
when attempting to debug or program the device. This can be done using a 0Ω resistor, which is mounted by default
and removed or replaced by a pin header while debugging. This configuration effectively means that programming
should be done before mounting the device.
Power Debugger
On-chip Debugging
©
2020 Microchip Technology Inc.
User Guide
DS40002201A-page 68
