User manual

Atmel-ICE [USER GUIDE]
42330A-MCU-07/2014
20
When designing an application PCB which includes an Atmel AVR with the JTAG interface, it is recommended
to use the pinout as shown in Figure 4-2, “AVR JTAG Header Pinout” on page 20. The Atmel-ICE can
connect to both 100-mil and 50-mil variants of this pinout.
Figure 4-2. AVR JTAG Header Pinout
GND
VCC
/RESET
(TRST)
GND
TCK
TDO
TMS
TDI
1 2
AVR JTAG
(NC)
Table 4-1. AVR JTAG Pin Description
Name Pin Description
TCK 1 Test Clock (clock signal from the Atmel-ICE into the target device).
TMS 5 Test Mode Select (control signal from the Atmel-ICE into the target device).
TDI 9 Test Data In (data transmitted from the Atmel-ICE into the target device).
TDO 3 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 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 Target voltage reference. The Atmel-ICE samples the target voltage on this pin in
order to power the level converters correctly. The Atmel-ICE draws less than 3mA
from this pin in debugWIRE mode and less than 1mA in other modes.
GND 2, 10 Ground. Both must be connected to ensure that the Atmel-ICE and the target device
share the same ground reference.
Tip
Remember to include a decoupling capacitor between pin 4 and GND.
When designing an application PCB which includes an Atmel SAM with the JTAG interface, it is recommended
to use the pinout as shown in Figure 4-3, “SAM JTAG Header Pinout” on page 20. The Atmel-ICE can
connect to both 100-mil and 50-mil variants of this pinout.
Figure 4-3. SAM JTAG Header Pinout
TMS
TCK
TDO
TDI
nRESET
VCC
GND
GND
(KEY)
GND
1 2
SAM JTAG
Table 4-2. SAM JTAG pin description
Name Pin Description
TCK 4 Test Clock (clock signal from the Atmel-ICE into the target device).
TMS 3 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.