SAMA5D3x-EK User Guide
6-9
11180A–ATARM–30-Jan-13
6.2.3.1
Disabling J-Link-OB-SAM3U128
The J-Link-OB-ATSAM3U4C may be disabled by Jumper JP15 (PA26, pin 25 of the ATSAM3U4C CPU).
Jumper not fitted: J-Link-OB-ATSAM3U4C is enabled and fully functional
Jumper fitted: J-Link-OB-ATSAM3U4C is disabled
The pin uses internal pull-up (so if JP15 is not required, simply leave the pin on the J-Link-OB-
ATSAM3U4C open), jumper shortens to ground. If J-Link is disabled, serial COM port via CDC is still
functional.
Disabling the jumper is not required to use the external debugger since target interface (JTAG/SWD)
remains disabled until first target communication takes place.
6.2.3.2
Hardware UART via CDC
J-Link-OB-ATSAM3U4C comes with an additional hardware UART that is accessible from a host via
CDC which allows terminal communication with the target device. This feature is enabled only if a certain
port (CDC disabled, PA25, pin 24 on J-Link-OB-ATSAM3U4C) is NOT connected to ground (open).
Jumper JP16 not fitted: CDC is enabled
Jumper JP16 fitted : CDC is disabled
6.2.4
USART
The USART1 is used as a user serial communication port. This USART is buffered with an RS-232
Transceiver (TXD, RXD and handshake CTS/RTS control) and connected to the DB-9 male socket. The
software must assign the appropriate PIO pins to enable the USART function.
Figure 6-7.
USART1 Com Port
RTSC1
TXDC1
CTSC1
RXDC1
EARTH_RS232
VDDIOP1
VDDIOP1
PB27
PB29
PB28
PB26
PB31
PB30
USART1
RTS1
TXD1
CTS1
RXD1
DRXD
DTXD
R23
47k
R23
47k
C19
100n
C19
100n
J8
J8
5
4
3
2
1
9
8
7
6
10
11
R132
0R
DNP
R132
0R
DNP
C15
100n
C15
100n
C17
100n
C17
100n
R28
0R
R28
0R
C14
100n
C14
100n
C13
4.7u
C13
4.7u
C18
100n
C18
100n
R31
0R
R31
0R
R133
0R
DNP
R133
0R
DNP
R30
0R
R30
0R
L5
220ohm at 100MHz
L5
220ohm at 100MHz
1
2
MN4
ADM3312EARU
MN4
ADM3312EARU
V+
1
C2+
2
VCC
3
C2-
4
EN
5
C1+
6
T1IN
7
T2IN
8
T3IN
9
R1OUT
10
R2OUT
11
R3OUT
12
R3IN
13
R2IN
14
R1IN
15
T3OUT
16
T2OUT
17
T1OUT
18
SD
19
C1-
20
V-
21
C3-
22
GND
23
C3+
24
R27
0R
R27
0R
R22
47k
R22
47k
C16
100n
C16
100n
R29
0R
R29
0R
R24
47k
R24
47k
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