Appendix A. Using the Handshaking Lines for General Input/Output
A-2
A.2 The Output Pin (RTS/Pin 8)
To set the output pin (RTS/pin 8) you must use the
SerialOutBlock()
instruction.
The spare I/O lines are RS-232 lines, NOT logic lines. This means that the
output line voltage is –12V and +12V (approximately), not 0 and 5V.
The following examples show you how to set the output pin using the
SerialOutBlock()
instruction.
CRBasic example for setting the output pin
SerialOutBlock(32, 1, 0) ' This will set the spare output pin high
SerialOutBlock(32, 0, 0) ' This will set the spare output pin low
The two example lines of code above will set the output pin on the
SDM-SIO1A high then low respectively on the SDM-SIO1A device set to
address 0 on its rotary switch.
Any value greater than 1 will set the output pin high, but usually the number 1
is used, as this will improve the readability of the code.
Value of SerialOutBlock
SerialExpression variable
Voltage on the output line
1
+12V
1
0
–12V
1
1
Approximate voltage; do not drive relays or high current loads directly from this pin.