BitBlt Co-Processor
BITBLT is an acronym for bit block level transfer. The Hornet BitBlt block is a
specialized co-processor designed to accelerate bit-mapped block transfers into the CGA
compatible graphics frame-buffer. It operates as a DMA co-processor where the transfer
is set up and then enabled by the CPU. The BitBlt block then obtains control of the bus
from the CPU and performs the transfer.
This BitBlt is rather limited in its capabilities. It supports the following
features/limitations:
- Horizontal sizes in even numbers from 2-16 pixels are supported.
- Vertical sizes from 1-32 pixels are supported.
- Characters must be placed horizontally on even bit boundaries.
- Clipping is marginally supported.
- 16 transfer modes allow any logical function of source and destination.
- "Insane" font table format of display controller is supported.
- Transfers are only supported to CGA compatible graphics frame buffers.