4.3.3 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 Debug header. The connector should be selected based on the pinout of the target board, and not the target MCU type - for example, a SAM device mounted in an AVR STK600 stack should use the AVR header.
The recommended pinout for the 10-pin AVR JTAG connector is shown in Figure 4-6.
The recommended pinout for the 10-pin Arm Cortex Debug connector is shown in Figure 4-2.
Direct Connection to a Standard 10-pin 50-mil Header
Use the 50-mil 10-pin flat cable (included in some kits) to connect directly to a board supporting this header type. Use the AVR connector port on the Atmel-ICE for headers with the AVR pinout, and the SAM connector port for headers complying with the Arm Cortex Debug header pinout.
The pinouts for both 10-pin connector ports are shown below.
Connection to a Standard 10-pin 100-mil Header
Use a standard 50-mil to 100-mil adapter to connect to 100-mil headers. An adapter board (included in some kits) can be used for this purpose, or the JTAGICE3 adapter can be used for AVR targets.
The JTAGICE3 100-mil adapter cannot be used with the SAM connector port since pins 2 and 10 (AVR GND) on the adapter are connected.
Connection to a Custom 100-mil Header
If your target board does not have a compliant 10-pin JTAG header in 50- or 100-mil, you can map to a custom pinout using the 10-pin “mini-squid” cable (included in some kits), which gives access to ten individual 100-mil sockets.
Connection to a 20-pin 100-mil Header
Use the adapter board (included in some kits) to connect to targets with a 20-pin 100-mil header.
| Name | AVR PORT Pin | SAM PORT Pin | Description |
|---|---|---|---|
| TCK | 1 | 4 | Test Clock (clock signal from the Atmel-ICE into the target device) |
| TMS | 5 | 2 | Test Mode Select (control signal from the Atmel-ICE into the target device) |
| TDI | 9 | 8 | Test Data In (data transmitted from the Atmel-ICE into the target device) |
| TDO | 3 | 6 | Test Data Out (data transmitted from the target device into the Atmel-ICE) |
| nTRST | 8 | - | Test Reset (optional, only on some AVR devices). Used to reset the JTAG TAP controller |
| nSRST | 6 | 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 | 4 | 1 | Target voltage reference. The Atmel-ICE samples the target voltage on this pin to power the level converters correctly. The Atmel-ICE draws less than 3 mA from this pin in debugWIRE mode and less than 1 mA in other modes. |
| GND | 2, 10 | 3, 5, 9 | Ground. All must be connected to ensure that the Atmel-ICE and the target device share the same ground reference. |