Interrupts and Activity Monitors

There is one interrupt and one activity monitor associated with the display controller. DCINT, the display cursor interrupt, is used by software to keep the cursor in the visible part of a zoomed text mode. DBA, the display buffer activity monitor, is used by software to tell when its safe to go into light sleep.

DCINT is triggered by writes to the cursor address registers at indexes -0Eh and -0Fh within the CRTC. DCINT will be disabled if the CRTC registers are disabled by the DspEnable bit in the DspSetUp register. If the CRTC registers are enabled the CRTC's address is controlled by the CGAMode bit in the DspSetUp register. DCINT is also controlled by the Hornet interrupt system. See "Interrupt Control" on page 15-554 for more details.

The DBA monitor is triggered by reads or writes to the display frame buffer. DBA will be disabled if the DspEnable bit in the DspSetUp register is clear. The address of the frame buffer is controlled by the CGAMode bit in the DspSetUp register. The DBA monitor is located in the system status register. See "Power Management" on page 16-563 for more information.