of lines per field (up to 1024). The address of the
display viewport (this part of the display memory to
be actually displayed on the screen) is fully pro-
grammable. The display processor provides the
display dynamic RAM refresh (see video timing
generator section for details).
I.3.2 - DRAWING AND ACCESS COMMANDS (R0
to R3, R12 to R23).
The 16 remaining registers are used to specify a
comprehensive set of commands. The highly or-
thogonal drawing command set allows the user to
”draw” in the display memory such basic patterns
as lines, arcs, polylines, polyarcs, rectangles and
characters. Efficient procedures are available for
either area filling and tiling or line drawing and
texturing. Lines may be drawn with a PEN in order
to get thick strokes. Any drawing is specified in a
2
13
x 2
13
drawing coordinate system.
To access the display memory, the host microproc-
essor has an indirect, sequential access to any
”window”. Access commands can be used to load
the character generators as well as to load or save
arbitrary windows stored in the frame buffer.
I.4 - Data Type Definitions
PIXEL : this is the smallest color spot displayable
on the CRT.
PEL : a Picture Element is the coding of a PIXEL in
the display memory. The TS68483 can handle 4
different PEL formats :
- 4 color bits - short
- 4 color bits + 1 mask bit - short masked
- 8 color bits - long
- 8 color bits + 1 mask bit - long masked
DRAWING COORDINATES : (see Figure 2)
The drawing commands are specified and com-
puted in a 2
13
x 2
13
cyclical coordinate system. The
drawing coordinates are clipped and mapped into
the 2
11
x 2
11
display memory addressing space.
Further clipping to the actual frame buffer size may
be performed by the user designed memory inter-
face.
DISPLAY MEMORY :
This is the dedicated memory to the display unit.
This memory is addressed as four banks of 4-bit
plane each.
BIT PLANE :
Each bit plane has a maximum capacity of 2
11
x 2
11
bits. A byte wide organization of each bit plane is
required.
MEMORY ADDRESS : (see Figure 3).
In order to address one bit in the display memory,
the user must specify :
- A bank number (2 bits) B = 0 to 3
- A bit plane number (2 bits) Z = 0 to 3
- A Y address (11 bits) Y = 0 to 2047
- An X address (11 bits) X = 0 to 2047
MEMORY WORD : (see Figure 3)
A 32-bit memory word can be either read or written
during each memory cycle (8 CLK periods), one
byte at a time in each bit plane in the addressed
bank. The memory bandwidth is in the 6 to 8Mby-
tes/s range.
VIEWPORT :
This is any rectangular array of pels located in the
display memory.
FRAME BUFFER :
This is the biggest viewport which can be held in
the display memory. The frame buffer maps a
window at the origin of the drawing coordinates. A
short pel frame buffer may be located in any bank.
A long pel frame buffer must be located in the ”bank
0, bank 1” pair.
DISPLAY VIEWPORT :
This is the viewport which is displayed on screen.
MASK BIT PLANE :
When masked pels are used, a mask bit plane must
be associated to a frame buffer. Mask bit planes
may be located in any plane of bank 3.
CELL :
A CELL is any pattern stored in the display memory
as a rectangular array of bit mapped elements. The
drawing of any CELL may be specified with a
scaling factor.
CHARACTER :
This is a one bit per element CELL. It may be stored
in any bit plane, then colored and drawn in a frame
buffer by use of PRINT CHARACTER command.
OBJECT :
This is a one short pel per element CELL. It may
be drawn or loaded in a frame buffer.A source mask
bit may be associated to each element. An OB-
JECT may then be printed in another location by
use of a PRINT OBJECT command.
PEN :
This is the pattern which is repeatedly drawn along
the coordinates defined by either a LINE or an ARC
command.
The PEN may be a DOT (single pel), a CHARAC-
TER or an OBJECT.
TS68483A
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