Appendix A. Using the Handshaking lines for general input/output
A-2
The input line can accept 0 and 5V logic inputs OR -12 and +12V RS232 level
inputs. Below is a break down of the different input voltages allowed and the state
of the input line flag.
Voltage on the input line
State of bit 16
+12V
1
-12V
0
5V
1
0V
0
A.2 The output pin (RTS/pin 9)
To set the output pin (RTS/pin 9) you must use the ‘SerialOutBlock’ command.
The spare I/O lines are RS232 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-SIO1
high then low respectively on the SDM-SIO1 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
