S42 Hardware User Guide
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Page 36 of 62
Notes:
(1)
a discrete pull up resistor is used
(3)
function depends on firmware
(4)
DNU: Do Not Use, Do Not Connect
(6)
signal must be accessible for homologation purposes. Refer to 3.9 Test Mode
(7)
signals sampled at startup time. TESTMODE# is I-PU, BOOT0 is I-PD during sampling time only, I-DIS otherwise
(8)
Pin Type depends on UICP status. Refer to 3.3.4 Dynamic I/O Signal Type Changes depending on the UICP status
(9)
for compatibility to SR this pin is reserved for an external antenna and must be left open
Table 8: Application Specific Pin Assignments, TIO
4.3
Handling of Unused Signals
Depending on the application, not all signals of S42 may be needed. The following
list gives some hints how to handle unused signals.
•
EXT-RES#
If no external Reset is needed: Leave open
•
BOOT0
leave open
(1)
•
XL-IN
If no external XTAL is connected: Leave open
•
XL-OUT
If no external XTAL is connected: Leave open
•
UART-RXD, UART-TXD
If UART is not used: On UART-RXD, add a
pullup (e.g.100k
Ω) to VSUP
(1)
; leave UART-TXD open
(1)
•
UART-RTS#, UART-CTS#
If neither flow control nor UICP is used:
Leave open
(1)(2)
•
IUR-OUT#, IUR-IN#
If UICP is not used: leave open
•
NFCANT1, NFCANT2 If no NFC antenna is connected: Leave open
•
TESTMODE#
Leave open
(1)
•
unused GPIOs
Leave open
•
SWDIO, SWCLK
Leave open. Only needed for debug
purposes.
Please note, to keep compatibility with future feature enhancements, unused signals shall not
be connected directly to VSUP or GND. Leave open.
Notes:
(1)
Signals must be accessible during the homologation process, refer to 3.9 Test Mode.
(2)
It is strongly recommended to use hardware flow control in both directions.
Not using flow control can cause a loss of data.