Manual

8-2 Using the Digital Outputs and Inputs
For example, suppose you have connected a relay to Digital Output 0, and suppose the relay
needs 0.01 seconds to close and 0.02 seconds to open. When you send CD 1; the relay
closes; CD 0; opens it. If you first send WD .02; the System automatically waits .02
seconds after any CD command. If you would rather, you can save .01 seconds now and
then by using pairs of commands: CD 1; WA .01; and CD 0; WA .02; .
Getting Fancier
Now suppose you need to change the Digital Outputs while the motors are moving. The
classic example of this is a fluid-dispensing system: a small pipette is attached to the
carriage. A solenoid- operated valve starts and stops the fluid flow through the pipette, with
some consistent but unavoidable delay in response.
In order to avoid a gap in dispensed fluid at the beginning of each move, the valve must turn
on a short while before the carriage begins to move. And in order to avoid getting a blob of
fluid at the end of each move, the valve must turn off before the carriage has come to rest.
The solution here is the PD command and the MD or MM command. Use PD to set up a
valve turn-on and delay. Then decide how far before the end of the move, to turn off the
valve, and send an MD or MM command with a negative <count> to turn it off just before
the end. The same PD and MD/MM will work equally well for vectors, arcs, and
Continuous Path moves.
If you have an occasional move in which you don't want to dispense any fluid, just use the
VM ("Vector Mode") command to temporarily disable the PD and MD commands, and
perhaps even to speed up the motors. VM needs fewer characters to transmit (and less
download memory) than PD and MD/MM, and executes faster within the Automove System.
If you need more than two changes in a single move, use the MM command instead of the
MD command.
Reading Them Back
The OD command allows your host software to read back the current state of the Digital
Outputs. This might be useful if, for example, you have several host programs which need
to work together in controlling the same Outputs; or if the host software needs to see which
state the Outputs were left in by a TD command.
Don't confuse the OD command with the ON command, which reads the Digital Inputs.
The Digital Inputs
The Digital Inputs are eight logic inputs tied to a back-panel connector. For the connector
pinout and electrical specifications see the Automove Operation manual.
There are eight ways to use the Digital Inputs:
1. Your host computer can test the state of the inputs by using the ON ("Output Digital Inputs
State") command.