MB87P2020 Datasheet, PDF (202/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

MB87J2120, MB87P2020-A Hardware Manual
shown in figure 5-2. It is quite similar to that in figure 5-1. Segment length is determined using equation
(17).
MaxSegWords := 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_words := 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)
if logical_color_space(l) == YUV422 then
layer_stop := layer_stop + 1
seg_words := seg_words +
truncate((layer_stop - layer_start + ppw_log(l)-1) / ppw_log(l))
end
if seg_words > MaxSegWords then
MaxSegWords := seg_words
end
Figure 5-2: Algorithm to determine the maximum number of words fetched per segment.
With this result, condition (25) is refined to
T _{seg, out} ≥ T _CoreClock ⋅ (W _{peak, GPU} + W _{peak, other units})
(26)
Where T_{seg, out} is the time to output one segment as calculated in equation (19), and W_{peak, GPU} is simply
MaxSegWords.
5.3 Recommendations
In order to ensure correct GPU function it is important to estimate the necessary bandwidth for pixel
processing and output. However, one has to bear in mind that not all influences are known in advance, es-
pecially the behaviour of other units the GPU shares the SDC and VideoRAM with. Therefore, one should
provide for sufficient safety range when determining GDC setup.
There are some issues that can help save memory and processing bandwidth. Following the recommenda-
tions given below it may be possible to operate at lower core clock / display clock ratios, thus improving
EMC and reducing power consumption.
• When the whole display area is covered by non-transparent layer pixels background painting can be
switched off.
• Multiple layers do not increase bandwidth when they do not cover each other.
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