Write-Per-Bit Registers; Vram Color Register And Block Fill Special Function; Display Memory Size - Rastergraf VFX-M User Manual

Rastergraf
The VRAM output shift registers supply 128 bits of pixel data every shift
clock to the TVP3030. Depending on the pixel size, this corresponds to
sixteen 8-bit pixels, eight 16-bit pixels, or four 32-bit pixels.
The data transfer operation has to be repeated only two or three times, at
most, during a raster line time. The VRAM is available for random access
operations at all other times. There is a small additional overhead time for
memory refresh, which occurs about once every 15 us. VRAM availability
for external access is about 95% as compared to about 35% for DRAM.
The VFX-M uses TI TMS55161 256K x 16 2-port EDO VRAM.

Write-per-bit Registers

VRAM has a write-per-bit feature that allows bit planes to be selectively
write enabled. This feature allows the I128S2 to perform write operations
instead of read-modify-write operations, which can be a significant
performance enhancement. When updated, the I128S2 write-per-bit
register contents are automatically stored in the VRAM using the
persistent write-per-bit function. The write-per-bit register has no effect on
the Pixmap (DRAM) Memory.

VRAM Color Register and Block Fill Special Function

The I128S2 can use the VRAM block write and color register special
functions. The color register is used in conjunction with the VRAM block
fill mode to enable up to 4 adjacent locations in the VRAM to be written
in one cycle. In this way, one can quickly replicate 1-D and 2-D patterns
in memory at up to 16 times the single pixel rate. Using block write, up to
64 (16 byte data bus * 4 locations/block) 8-bit pixels can be written in
each 40 ns page mode cycle, resulting in a 1600 Mpixel/sec FILL time.

Display Memory Size

The pixel size programmable to 8, 16, or 32 bpp. Although the RAMDAC
supports packed 24-bit mode, the I128S2 does not. The VRAM on the
VFX-M can be either 4 MB (4,194,304 bytes) or 8 MB (8,388,608 bytes).
You can calculate the possible display formats based on these values.
Note that you can render into VRAM that is not being used in the active
display, and by changing the starting address register in the I128S2, pan to
it so it is visible or BitBLT the Pixmap data to a static display window.
Troubleshooting 4-5
Artisan Scientific - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisan-scientific.com