SAM JTAG Pinout (Cortex®-M debug connector)

When designing an application PCB which includes a Microchip SAM with the JTAG interface, it is recommended to use the pinout as shown in the figure below. Both 100-mil and 50-mil variants of this pinout are supported, depending on the cabling and adapters included with the particular kit.

Figure 1. SAM JTAG Header Pinout

Table 1. SAM JTAG Pin Description
Name Pin Description
TCK 4 Test Clock (clock signal from the Atmel-ICE into the target device)
TMS 2 Test Mode Select (control signal from the Atmel-ICE into the target device)
TDI 8 Test Data In (data transmitted from the Atmel-ICE into the target device)
TDO 6 Test Data Out (data transmitted from the target device into the Atmel-ICE)
nRESET 10 Reset (optional). Used to reset the target device. Connecting this pin is recommended since it allows the Atmel-ICE to hold the target device in a Reset state, which can be essential to debugging in certain scenarios.
VTG 1 Target voltage reference. Atmel-ICE samples the target voltage on this pin to power the level converters correctly. The Atmel-ICE draws less than 1 mA from this pin in this mode.
GND 3, 5, 9 Ground. All must be connected to ensure that the Atmel-ICE and the target device share the same ground reference.
KEY 7 Connected internally to the TRST pin on the AVR connector. Recommended as not connected.
Tip: Remember to include a decoupling capacitor between pin 1 and GND.