6.3.1.7 SerialInChk()
This returns the number of characters that have been received by the SDM-SIO2R and that are
currently held in its buffer (0-6143).
6.3.1.8 SerialInRecord()
No special information.
6.3.1.9 SerialFlush()
This instruction will purge all information in the data logger and SDM-SIO2R transmit and receive
buffers.
7. Operation
This section includes more detail on less common modes of operation, provides details on how
to save power use, and shows the internal configuration of the SDM-SIO2R when configured in
RS-485 or RS-422 full-duplex mode.
7.1 Configuring handshaking and receive-
only modes
7.1.1 Using RTS/CTS and automatic handshaking
Handshaking is a method used by RS-232 to ensure communications equipment is free to
receive or transmit data. This interface is often called RTS/CTS (hardware handshaking) or
DTR/DTE.
Automatic handshaking for the SDM-SIO2R is activated through use of the
BaudRate
parameter of the
SerialOpen()
instruction.. When the
BaudRate
value is set to a negative
number, the SDM-SIO2R will enable automatic handshaking. It is worth noting that normally
setting the
BaudRate
to a negative number will enable automatic baud rate detection; this is
not the case for the SDM-SIO2R.
When enabled, the two I/O ports will operate as RTS and CTS lines. It is important that the remote
equipment supports handshaking as no data will be sent if handshaking is enabled but is not
supported by the equipment the SDM-SIO2R is connected to.
Once handshaking is enabled, these pins are no longer available for general use and are
dedicated to the auto-handshaking system.
SDM-SIO2R Serial Input/Output Module with Switched Sensor Power
34
