The attadc.sch schematic

A gensub record co-ordinated the sequence of XYCOM-240 inputs/outputs that are required to acquire a photodiode reading. Input J of the gensub record holds the current record state (a state machine is implemented in the gensub "snam" code), and triggering of a photodiode reading should be initiated by writing the integer value "1" (state 1) to this field.

• The output to trigger a read of the ADC is pulsed low for a fixed time. This is acheived using binary output "bo1".
• After this trigger, the record expects to see that the value from binary input "bi" has gone low, to signal that the hardware has an ADC reading available. If so, the record collects the ADC reading from the "mbi" multi-bit binary output record. This is presented on gensub output OUTA for use by other records.
• The output from binary output "bo2" is pulsed low for a fixed time, after which the value from binary input "bi" should have returned high. The hardware has been reset.
• The gensub record then returns to state zero. At this point another reading cycle can be triggered by restarting in state 1 (writing "1" to the gensub input J).