| UK Astronomy Technology Centre | Chris Tierney |
| Royal Observatory, Edinburgh | 31st March 2001 |
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.The filter assembly consists of a single filter wheel. Filters are selected by rotating the wheel to one of six positions. The wheel motor is controlled from a single deviceControl record. Higher level control is implemented using the filter assemblyControl record.
INDEXing the filter assembly causes the assemblyControl record to forward an "ixhome" target position to the filter wheel device. This named position is defined in the lookup table for the device, wheel_device.lut, and instructs the device to index using algorithm 1 (see documentation on the deviceControl screen for detail).
During a MOVE operation, the assembly looks at the string in input field A (where the user should place the demand position) to see if it can be converted to a numerical value. If so, the value is forwarded to the device as a target position. If not, the record compares the string with the list of named filter wheel positions contained in the filter assembly lookup table, filter_assembly.lut. If the string is found in the list, it is converted to a position in engineering units (degrees) and forwarded to the device. If the string is neither numeric nor known to the record, the MOVE operation is rejected.
Named positions are defined for each of the six filter wheel positions.
The binary input record "ilck" is used to interlock the filter assembly. This (boolean) signal is forwarded, via a fanout record, to both the assemblyControl (ILCK field) and deviceControl (FLT field) records. Upon receipt of a non-zero value at the FLT field, the device will immediately stop all motion of the motor. 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.