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SDM-SIO1A Serial Input/Output Module
4.1.7 SerialInChk
4.1.8 SerialInRecord
4.1.9 SerialFlush
4.1.10 Serial Input Errors
4.2 Configuring handshaking and receive only modes
4.2.1 Using RTS/CTS and automatic handshaking
18
This returns the number of characters that have been received by the SDM-SIO1A
and that are currently held in its buffer (0-6143).
No special information.
This command will purge all information in the logger and SDM-SIO1A transmit
and receive buffers.
For any of the serial input instructions above, the character '?' will be returned in
place of the expected data whenever a parity, framing or overrun error is detected.
These errors are only flagged for RS-232/RS-485/RS-422 data coming into the
SDM-SIO1A. A large number of such characters could indicate an incorrectly
setup protocol configuration using the SerialOpen command, or one of the wires is
loose or incorrectly terminated.
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-SIO1A is activated through use of the
'SerialOpen' commands 'BaudRate' setting. When the 'BaudRate' value is set to
a negative number the SDM-SIO1A 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-SIO1A.
When enabled the two I/O ports (pins 8 and 11) 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 the
SDM-SIO1A is connected to.
Once handshaking is enabled pins 8 and 11 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 within this manual.
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