S42
Hardware User Guide
1VV0301303 Rev. 11
Page 16 of 85
2021-05-06
Not Subject to NDA
Sx
IUR-IN / DTR
IUR-OUT / DSR
IUC-IN / RTS
IUC-OUT / CTS
Rx-Data
Tx-Data
Host
DTR / IUR-IN
DSR / IUR-OUT
RTS / UIC-IN
CTS / IUC-OUT
Rx-Data
Tx-Data
Figure 4: Connection Sx to Host
All
signal
pairs,
•
TX-Data / RX-Data,
•
(IUC_IN/RTS) / (IUC-OUT/CTS)
•
(IUR-IN/DTR) / (IUR-OUT/DSR)
must be
connected
crosswise between the 2 devices.
Note/Tip: It is strongly recommended to use hardware flow control
in both directions. Not using flow control can cause a loss of data
3.3.1.
Serial Interface HW Configuration for Power Management
Note/Tip:
It is strongly recommended NOT to switch the module power supply
on/off while other parts of the circuitry stay powered. This mostly
leads to hardly controllable back-feeding issues. Back-feeding
occurs due to connected signal line(s) being >0,3V while the module
power is switched off. Then the I/O protection diodes, integrated in
the I/O ports of the BT IC, will feed the VSUP “backwards”, which
means that the modules power supply is fed via the I/O lines instead
via the power supply. Due to the ultra-low power design a few µAmps
are enough to raise VSUP to an undefined state, which may cause a
hang-up deadlock when then power is switched on again.
Any I/O pin at a voltage > 0,3V while the supply VSUP is at 0V violates
the abs. max. ratings given in chapter 5.1 Absolute Maximum
Ratings.
It is instead recommended to use the advanced power management
features, which may reduce the supply current to 300nA.
