MB87P2020 Datasheet, PDF (200/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

MB87J2120, MB87P2020-A Hardware Manual
b) Maximum time to process a segment:
max(T _{seg, proc}) = T _CoreClock ⋅ MaxSegPixel
(22)
To obtain the value MaxSegPixel the segment with the maximum number of pixels processed has to be
found. This is achieved following the algorithm shown in figure 5-1.
MaxSegPixel := 0
for y := 0 to (PhysSizeY-1) do
begin
act_layers:= {}
foreach l in vis_layers do
begin
if y >= OffsY(l) and y < (OffsY(l)+WY(l)) then
act_layers := {act_layers, l}
end
if act_layers == {} then continue
segm_start := 0
while (segm_start < PhysSizeX) do
begin
segm_stop := min((segm_start + SegLen), PhysSizeX)
seg_pixels := 0
foreach l in act_layers do
begin
if OX(l) >= segm_stop or (OX(l) + WX(l)) < segm_start then
continue
if OX(l) < segm_start then
layer_start := segm_start
else
layer_start := OX(l)
if (OX(l) + WX(l)) >= segm_stop then
layer_stop := segm_stop
else
layer_stop := OX(l) + WX(l)
seg_pixels := seg_pixels + (layer_stop -layer_start)
end
if logical_color_space(l) == YUV422 then
seg_pixels := seg_pixels + 2
if background_enabled then
seg_pixels := seg_pixels + (segm_stop - segm_start)
if seg_pixels > MaxSegPixel then
MaxSegPixel := seg_pixels
end
Figure 5-1: Algorithm to determine the maximum number of processed pixels per line segment.
As a result of this the minimal frequency ratio of core clock to display clock is derived as:
----^f---^C--^o---^r-^e--^C---^l-^o--^c--^k--- =
f _DisplayClock
T_{-----D---i-s-p--l--a--y--C--l--o--c--k}
T _CoreClock
≥
M_------a_---x_--S_---e_---g_---P_----i_-x_---e_---l
SegLen
⋅
ScanFactor
(23)
5.2 Memory Bandwidth
Although memory access is more unlikely to become the bottleneck in contrast to processing it may turn
out as limiting factor when memory traffic of other GDC units (e.g. Pixel Processor or Direct Access) in-
creases. Therefore, estimations for memory bandwidth are given here.
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