UK Astronomy Technology Centre	Chris Tierney
Royal Observatory, Edinburgh	31st March 2001

The adc.sch schematic

Links from the schematic:

The CAD and CAR records on this schematic are not used. They were included for compliance with Gemini interface standards that was eventually deemed not required on NAOMI.

Upon receipt of a "go" directive in INDEX mode, the assembly forwards "ixhome" named positions to each of its attached devices. These named positions are defined in the lookup tables for the devices, adc1_device.lut and adc2_device.lut, and instruct the devices to use index algorithm 1 (index to home switch).

When performing a MOVE operation, the assembly examines input fields A and B for numerical values. These are the required (demanded) angle of the first ADC prism and the offset angle from this to the second ADC prism. Both are specified relative to a defined, zero dispersion, configuration for the assembly. Accordingly, the target angles for the two stages are calculated thus:

(target angle for prism 1) = (demand prism 1 angle) + (prism 1 offset angle)

(target angle for prism 2) = (demand prism 2 angle) + (prism 2 offset angle) + (demand prism 1 angle)

The recognised named positions for the demand angle and offset are defined in the lookup table for the ADC assemblyControl record, adc_assembly.lut, the most useful being "center" (which has a numerical equivalent of zero).

The offset angles are also defined in this lookup table file, using the named parameters "adc1offset" and "adc2offset".

The binary input record "ilck" is used to interlock the ADC assembly. This (boolean) signal is forwarded, via a fanout record, to the assemblyControl (ILCK field) and deviceControl (FLT field) records. Upon receipt of a non-zero value at the FLT field, the devices will immediately stop all motion of the ADC prism motors. The assembly will stop any operation it is current engaged in. Normal operation can be resumed by restoring the interlock signal to its default (zero) value.