BlueMod+S50 Hardware User Guide
1VV0301505 Rev. 1 Page 16 of 53 2018-03-02
4.3.2. 4-Wire Serial Interface
If the host in question is sufficiently fast, a four-wire scheme may be successful. Connect
the serial lines UART-RXD, UART-TXD as well as UART-RTS# and GND; leave UART-
CTS# open. The host is required to stop sending data within a short time after de-assertion
of UART-RTS# (there is room for up to 4 more characters at the time RTS# drops).
Figure 6: UART Interface without UICP Signals 4-wire (incl. GND)
UICP has to be deactivated permanently in this configuration, because
signal UART-CTS# and IUR-IN# become inputs with no PU or PD if
UICP is active. This would cause floating CMOS inputs.
It is strongly recommended to use hardware flow control in both
directions. Not using flow control can cause a loss of data.
4.3.3. Serial Interface with UICP
A substantially saving of power during idle phases can be achieved (see when the UICP
protocol is used (refer to [2]). This protocol should be implemented on the host side as well.
Signals IUR-IN# and IUR-OUT# should be connected to the host and may be mapped to
DSR and DTR, if an RS232-style (DTE-type) interface is used (see Figure 7).
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