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 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.
In addition, the Power Debugger also has an unpopulated 100-mil 10-pin JTAG connector in the AVR pinout on its PCB. This is wired directly to the 50-mil 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 Power Debugger 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 alternatively 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 Power Debugger into the target device). |
| TMS | 5 | 2 | Test Mode Select (control signal from the Power Debugger into the target device). |
| TDI | 9 | 8 | Test Data In (data transmitted from the Power Debugger into the target device). |
| TDO | 3 | 6 | Test Data Out (data transmitted from the target device into the Power Debugger). |
| 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 Power Debugger 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 Power Debugger samples the target voltage on this pin in order to power the level converters correctly. The Power Debugger 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 Power Debugger and the target device share the same ground reference. |