PCVisionplus
Hardware Reference
Theory of Operation
2–9
Rev 02; February 8, 2002
In 12-bit mode and zoom by 2, each WORD read from the image buffer memory is replicated twice in the BMC
before output to the PCI-bus, as shown in Figure 2–6. The transfer count must be doubled for zoom by 2. The data
output is twice the data read from the image memory.
In 12-bit mode and zoom by 4, each WORD read form the image buffer memory is replicated four times in the BMC
before output to the PCI-bus. It takes two 32-bit transfers to perform 12-bit zoom by 4. Figure 2–6 shows the first of
two transfers for the zoom by 4. The transfer count must be multiplied by four in zoom by 4. The data output is four
times the data read from the image memory.
Image Buffer Memory
pixel1
pixel1
pixel0
pixel0
Bus Master Controller Output
Zoom by 2
pixel0
pixel0
pixel0
pixel0
Bus Master Controller Output
Zoom by 4
lsb
msb
lsb
msb
7 ... 0
pixel6
7 ... 0
pixel5
7 ... 0
pixel4
7 ... 0
pixel3
7 ... 0
pixel2
7 ... 0
pixel1
7 ... 0
pixel0
Figure 2–5. Bus Master Zoom, 8-bit Mode
xxxx 11 ... 0
xxxx 11 ... 0
xxxx 11 ... 0
xxxx 11 ... 0
0
15
pixel0
pixel1
pixel2
pixel3
Image Buffer Memory
Bus Master Controller Output
xxxx 11 ... 0
pixel0
xxxx 11 ... 0
pixel0
lsb
msb
Figure 2–6. Bus Master Zoom 2, 12-bit Mode
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