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Chapter 7 Controllers

6. Menu Objects

Menus control enumerated or discrete channels only. They will not connect to analog channels, and will display an 'invalid database type' message when an analog channel is specified in their 'channel to control or monitor' property:

Invalid db_type
No val
Menus are used with channels that have a number of specific choices, binary channels, multi-bit binary channels, enumerated channels, or menu-choice channels (ENUM, RECCHOICE, GBLCHOICE). For example, if you specify the SCAN field of record as a channel for a menu object and if the operator holds down the right mouse button on that menu at run-time, he or she will see the possible choices for the SCAN fields: passive, event, I/O Intr,1 second, 0.5 second, and so on. If the menu were connected to the OMSL field of a record, the menu choices would be two: supervisory and closed_loop. You must have some familiarity with EPICS records to know all the channels which channels would be compatible with the menu object.

There is only one property unique to menus: the 'menu title' property, which is simply a string that labels the menu to aid the operator in recognizing the menu's purpose. You could enter in the channel name that the menu connects to or any other name that will help the operator identify the menu's purpose. If you do not specify anything in the 'menu title' property, the current setting of the menu, the last choice will be displayed, which can also be helpful.

Regarding the other properties in the menu's property sheet, the 'units modifier,' 'high display limit,' 'low display limit,' and 'label type' properties are insignificant for menus and have no effect on their run-time behavior or appearance. For more information about the other properties in the property sheet, see Chapter 4, Creating and Manipulating Objects. For more information about using menus at run-time, see Chapter 9, DM: Run-time Operation.

Menu for a SCAN Channel.

EDD/DM User's Manual, 2.4 - 27 MARCH 1997
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