S42
Hardware User Guide
1VV0301303 Rev. 11
Page 41 of 85
2021-05-06
Not Subject to NDA
4.6.
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.
Warning:
(1) Signals must be accessible during the homologation process,
refer to 3.10 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.