The F18A is a pin-compatible drop-in replacement for TI's TMS9918A family of video display processors, which include the TMS9918A, 9928, 9929, 9118, 9128, and 9129 chips. The design uses an FPGA (hence the 'F' in F18A) to implement the original functionality of the VDP, but it also contains many enhancements that new software can take advantage of. Some of the more interesting features include:
- Crisp VGA video output. The orignal 256x192 pixels are doubled to 512x384, with background color borders to fill out the 640x480.
- Implements the origianl 16K of VRAM in the FPGA's block RAM.
- No VDP over-running (can handle host access up to about 25MHz).
- All 32 sprites can be displayed on a single scan line, i.e. no more sprite flickering. All existing software immediately benefits from this feature.
- A 9938-compatible 80-column mode.
- Sixty-four 12-bit (4096 colors) palette registers.
- Per-tile properties such as x/y flip, palette select, priority over sprites, and transparency.
- Full horizontal and vertical scroll registers.
- Programmable 1x1, 1x2, 2x1, or 4x4 name table configurations to support scrolling.
- A complete second tile field with independent name tables and horizontal / vertical scroll registers.
- A complete TMS9900 CPU core running at 100MHz that has complete access to the 16K of VRAM, 2K of private RAM, all VDP registers, and palette registers.
For more details, see http://codehackcreate.com