Front Panel Markers All "Data Available" and "Edge Detect" marker bits are physically available via the HP E1459A front panel. These outputs are TTL/HC compatible and may be used to trigger other system-wide events or to provide logging information for statistical tracking or other performance analysis purposes.
Interrupt Driven or Polled Mode Operations
Interrupt Parsing
Interrupts may be programmatically disabled for both edge-detect and data-capture events. All registers remain active and valid and may be serviced on a polled mode basis.
Since the command module interrupt handler must service multiple, concurrently-occurring interrupts, (including those which may be sharing the same IRQ line), some method is necessary to ensure that only a single IRQ is posted by the HP E1459A during each service interval.
Individual interrupts must be serviced by a commander on a one-for-one basis. The HP E1459A accomplishes this by inhibiting the generation of a second IRQ each time an IRQ is posted. THE INHIBIT CONDITION IS CLEARED BY THE REMOVAL AND REASSERTION OF EITHER INTERRUPT ENABLE BIT, "DAV" OR "EDGE DETECT." (Refer to Figure 1-2.)
For this one-for-one interrupt parsing, the HP E1459A REQUIRES that a global interrupt enable, either DAV or Edge Detect, be disabled and reasserted within the context of the interrupt service procedure. Normally, you would simply shut off interrupts at the top of the service procedure, and would then re-enable them before returning from service. This is the suggested usage, although this specific sequence is not necessary for proper HP E1459A hardware function.
18 Installing and Configuring the HP E1459A
