S42
Hardware User Guide
1VV0301303 Rev. 11
Page 15 of 85
2021-05-06
Not Subject to NDA
The following table shows the pin states of S42 during reset active.
Pin Name
State: S42
EXT-RES#
Input with pull-up (1)
XL-IN
Input floating (disconnected)
XL-OUT
Input floating (disconnected)
UART-TXD
Input floating (disconnected)
UART-RXD
Input floating (disconnected)
UART-RTS#
Input floating (disconnected) with pull-up resistor 470k
Ω
(2)
UART-CTS#
Input floating (disconnected)
IUR-OUT#
Input floating (disconnected)
IUR-IN#
Input floating (disconnected)
GPIO[0:14]
Input floating (disconnected)
TESTMODE#
Input floating (disconnected)
BOOT0
Input floating (disconnected)
SWDIO
Input with pull-up (1)
SWCLK
Input with pull-down (1)
(1)
pull-up, pull-down: R
PU,
R
PD
is typ. 13k
Ω
(11k
Ω
to 16k
Ω
)
(2)
a discrete resistor is used
Table 3: Pin States during Reset
The pin states as indicated in Table 3 are kept until hardware initialization has started.
3.3.
Serial Interface
The serial interface of S42 is a high-speed UART interface supporting RTS/CTS
flow control and interface-up/down mechanism according to the UICP+ protocol (refer to
Electrical interfacing is at CMOS levels (defined by VSUP; see chapter 5.4.1).
Transmission speeds are 9600
–
921600 bps and 1Mbps (asynchronous).
Character representation: 8 Bit, no parity, 1 stop bit (8N1).
Hardware flow-control with RTS and CTS (active low).
Note/Tip: Transmission speed may be limited by firmware. See
corresponding AT command reference [3] for further information.
Note/Tip: Connecting Bluetooth module and host CPU via an UART
interface.