3.5.4
Debug Solution Selection
If the user does not require the on-board programming feature, this section can be left unpowered, with no impact on
the rest of the system. A level shifter has been placed on the DEBUG UART line (U29) between the SAMA7G5 MPU
and the on-board programmer (U26) to properly separate the two voltage domains.
Jumper JP5/J26 disables the J-Link-OB JTAG functionality. When installed (J26 shorted), a quad analog switch
(U25/U27) routes the JTAG interface of the SAMA7G5 to the 20-pin header J27.
• Jumper JP5/J26 not installed: J-Link-OB-ATSAM3U4C is enabled and fully functional.
• Jumper JP5/J26 installed: J-Link-OB-ATSAM3U4C is disabled and an external JTAG controller can be used
through the 20-pin JTAG port J27.
Figure 3-56. Debug Solution Selection Schematic
DEBUG SOLUTION SELECTION
0.1uF
10V
0402
C244
GND
VDD_3V3
GND
0.1uF
10V
0402
C246
JTAG_NTRST_PC25
JTAG_TCK_PC26
JTAG_TDI_PC28
JTAG_TDO_PC29
JTAG_TMS_PC27
JTAG_CONN_NTRST
JTAG_CONN_nRST
JTAG_CONN_TDI
JTAG_CONN_TMS
JTAG_CONN_TCK
JTAG_CONN_TDO
S
1
I0A 2
I1A 3
YA
4
I0B 5
I1B 6
YB
7
GND 8
YC
9
I1C 10
I0C 11
YD
12
I1D 13
I0D 14
E
15
VCC 16
IDTQS3VH257PAG
U25
DIS_JLINK
JLINK_TCK_IN
JLINK_TDI_IN
JLINK_TDO_IN
JLINK_TMS_IN
JLINK_nRST
JLINK_NTRST
100R
0402
5%
R253
nRST
JTAG_nRST
S
1
I0A 2
I1A 3
YA
4
I0B 5
I1B 6
YB
7
GND 8
YC
9
I1C 10
I0C 11
YD
12
I1D 13
I0D 14
E
15
VCC 16
IDTQS3VH257PAG
U27
GND
VDD_3V3
GND
GND
DIS_JLINK
10k
0402
1%
R261
GND
VDD_3V3_3U
DIS_CDC
10k
0402
1%
R260
GND
VDD_3V3_3U
1
2
HDR-2.54 Male 1x2
J26
1
2
HDR-2.54 Male 1x2
J25
JP4
JP5
B2 1
GND 2
VCCA
3 A2
4 A1
5
OE
6
VCCB 7
B1 8
TXS0102
U29
22R
0402 1%
R269
22R
0402 1%
R271
0.1uF
10V
0402
C270
GND
GND
VDD_3V3
0.1uF
10V
0402
C271
VDD_3V3_3U
DIS_CDC
JLINK_UART_TX
JLINK_UART_RX
0402
R270
0402
R272
DBGU_TX_PD16
DBGU_RX_PD17
In addition to the J-Link-OB functionality, the ATSAM3U4C microcontroller provides a bridge to a debug serial port
(DBGU) of the main board processor. The port is made accessible over the same USB connection used by JTAG by
implementing a Communication Device Class (CDC), which allows a terminal communication with the target device.
This feature is enabled/disabled by jumper J25.
• Jumper J25 not shorted: the J-Link-OB CDC function is enabled and fully functional.
• Jumper J25 shorted: the J-Link-OB CDC function is disabled.
The USB CDC converts the USB device into a serial communication device. The target device running the CDC is
recognized by the host as a serial interface (USB2COM, virtual COM port) without the need to install a special host
SAMA7G54-EK
Function Blocks
©
2022 Microchip Technology Inc.
and its subsidiaries
User Guide
DS50003273A-page 63