Campbell Scientific SDM-SIO1 Serial Input/Output Module - Manual (Page 25)

SDM-SIO1 Serial Input/Output Module
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-SIO1.
When enabled, the two I/O ports (pins 8 and 9) 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 isn’t supported by the
equipment connected to the SDM-SIO1.
Once handshaking is enabled pins 8 and 9 are no longer available for general
use and are dedicated to the auto-handshaking system.
Enabling handshaking will increase active current consumption due to the extra
RS-232 load. It will not affect sleep current however as the RS-232 chip is
disabled (sleep is set by calling the ‘SerialClose’ function).
For connection diagrams and further information on using handshaking consult
Section 3.3, Examples for Connecting the SDM-SIO1 to Other Equipment.
NOTE • Auto flow control should only be selected in RS-232 mode
• When Autoflow control is enabled the user can’t set or clear
the spare I/O ports (pins 8 and 9)
4.2.2 RS-485 Half-Duplex Mode
In RS-485, half duplex mode the SDM-SIO1 will wait for approximately 2.5
ms after a character is received before it tries to transmit data in the transmit
buffer. This is to insure that a contention does not occur on the data line which
will cause data corruption.
When in either RS-485 half duplex or full duplex modes the user
can’t set or clear the spare I/O ports (Pins 8 and 9). NOTE
4.2.3 Using the RS-232 Link in Receive Only Mode
To place the SDM-SIO1 into RS-232 receive only mode, use the SerialOpen()
instruction with the SerialOpenFormat value set within the range of 64 to 79.
Consult Section 4.1.1, SerialOpen(), for more detailed information about these
settings. In receive only mode the SDM-SIO1 will consume less current than
normal but still can receive new information on its RS-232 port.
The example below will set the SDM-SIO1 with the address 0 into receive only
mode. All normal baud rates and buffer sizes are supported.
Example
SerialOpen(32,115200,64,100,10000) ‘Set receive only mode
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