Brief description of the features of "OSCA"

OSCA is the default hardware configuration supplied for the V6Z80P's FPGA, but it is by no means fixed. Using the Xilinx Webpack software, the FPGA can be reconfigured to provide different features, or a totally new design EG: to emulate another system. The limitations are the components and connections provided on the PCB (such as the Z80 CPU, memory, oscillator and IO.)

Video:

OSCA has 3 main screen modes: Bitplane (planar Amiga-style) bytemap (linear VGA-style) and tilemap (8x8 and 16x16 tiles) - each allows 256 colours from a total palette of 4096. Other features include: Linedraw hardware, Blitter datacopy, Line sync'd co-processor, PAL / NTSC TV or VGA output. Additionally, 55 hardware sprites per scanline (16 pixels wide, 256 colours) can be displayed.

Audio:

There are four 8 bit audio channels (similar to the Amiga). Sample data is fetched from a 128KB area of system RAM via DMA.

Ports:

OSCA supports an SD card slot, a PS/2 keyboard and PS/2 mouse, an RS232 com port at 57600/115200 BAUD and 2 Atari 2600 / Amiga-style joysticks.

Z80 memory:

There is 512KB of system RAM. This is divided into 32KB pages which can be individually paged into the upper and lower halves of Z80 address space ($0000-$7fff and $8000-$ffff). This is achieved by writing to Z80 Port registers. The lower 32KB ($0-$7FFF) of Z80 address space also contains ranges of memory locations dedicated to video hardware etc, though these can be paged out to allow full access to the entire system RAM.