Arrangement for Automatic Switching Between Reading and Writing a Display Adapter Bit Map
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2005-Feb-19
An arrangement is described which allows more rapid update of bit map display memories. All-points-addressable (APA) display adapters allow software to control each pel (picture element) on a monitor. The APA display adapter that uses the arrangement disclosed here is used in an interactive environment to display text enclosed in windows. In the system in which the disclosed arrangement is used, it is much faster for the microprocessor to write to an I/O device than to read from it. This is because a write to the device will be overlapped with instruction fetches but a read from it will not be overlapped. A common operation in the environment in which the display adapter is used is to read data from one location in the bit map and write the data back to another location.