FT800 Series Programmer Guide
Version 2.1
Document Reference No.: BRT_000030 Clearance No.: BRT#037
81
Copyright © Bridgetek Limited
4
Display list commands
The graphics engine of FT800 takes the instructions from display list memory RAM_DL in
the form of commands. Each command is 4 bytes long and one display list can be filled
up to 2048 commands since the size of RAM_DL is 8K bytes. The graphics engine of the
FT800 performs respective operation according to the definition of commands.
4.1
Graphics State
The graphics state which controls drawing is stored in the graphics context. Individual
pieces of state can be changed by the appropriate display list commands (e.g.
COLOR_RGB) and the entire state can be saved and restored using the SAVE_CONTEXT
and RESTORE_CONTEXT commands.
Note that the bitmap drawing state is special: Although the bitmap handle is part of the
graphics context, the parameters for each bitmap handle are not part of the graphics
context. They are neither saved nor restored by SAVE_CONTEXT and
RESTORE_CONTEXT. These parameters are changed using the BITMAP_SOURCE,
BITMAP_LAYOUT, and BITMAP_SIZE commands. Once these parameters are set up, they
can be utilized at any display list until they were changed.
SAVE_CONTEXT and RESTORE_CONTEXT are comprised of a 4 level stack in addition to
the current graphics context. The table below details the various parameters in the
graphics context.
Table 3 Graphics Context
Parameters
Default values
Commands
func & ref
ALWAYS, 0
ALPHA_FUNC
func & ref
ALWAYS, 0
STENCIL_FUNC
Src & dst
SRC_ALPHA,
ONE_MINUS_SRC_ALPHA
BLEND_FUNC
Cell value
0
CELL
Alpha value
0
COLOR_A
Red, Blue, Green colors
(255,255,255)
COLOR_RGB
Line width in 1/16 pixels
16
LINE_WIDTH
Point size in 1/16 pixels
16
POINT_SIZE
Width & height of scissor
512,512
SCISSOR_SIZE
Starting
coordinates
of
scissor
(x, y) = (0,0)
SCISSOR_XY
Current bitmap handle
0
BITMAP_HANDLE