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R61509V Target Spec
Rev. 0.11 April 25, 2008, page 113 of 181
The VSYNC interface has the minimum for RAM data write speed and internal clock frequency, which
must be more than the values calculated from the following formulas, respectively.
iancevar)clocks(23))BP(BackPorch)FP(FrontPorch)NL(esDisplayLin(encyFrameFrequ
) [Hz] ency (fosclock frequInternal c
××++×=
fosc
1
)clocks(23)insargm)NL(esDisplayLin)BP(BackPorch(
)NL(esDisplayLin240
]Hz.)[(mineedRAMWriteSp
××−+
×
>
Note: When RAM write operation is not started right after the falling edge of VSYNCX, the time from
the falling edge of VSYNCX until the start of RAM write operation must also be taken into account.
An example of calculating minimum RAM writing speed and internal clock frequency in VSYNC interface
operation is as follows.
[Example]
Panel size 240 RGB × 432 lines (NL = 6’h35: 432 lines)
Total number of lines (NL) 432 lines
Back/front porch 14/2 lines (BP = 4h’E, FP = 4’h2)
Frame frequency 60 Hz
Internal clock frequency 678 kHz
Internal clock frequency (fosc) [Hz]
= 678 kHz
×
1.07 / 1.0 = 726 kHz
Notes: 1. When setting the internal clock frequency, possible causes of fluctuation must also be taken into
consideration. In this example, the internal clock frequency allows for a margin of ±7% for
variances and guarantee that display operation is completed within one VSYNCX cycle.
2. This example includes variances attributed to LSI fabrication process and room temperature.
Other possible causes of variances, such as differences in voltage change are not considered in
this example. It is necessary to include a margin for these factors.
Minimum speed for RAM writing [Hz]
>
240
×
432 / {((14
+
432 - 2) lines
×
23 clocks)
×
1/726 kHz} = 7.4 MHz
Notes: 1. In this example, it is assumed that the R61509V starts writing data in the internal RAM on the
falling edge of VSYNCX.
2. There must be at least a margin of 2 lines between the line to which the R61509V has just
written data and the line where display operation on the LCD is performed.
In this example, the RAM write operation at a speed of 7.4 MHz or more, which starts on the falling edge
of VSYNCX, guarantees the completion of data write operation in a certain line address before the
R61509V starts the display operation of the data written in that line and can write moving picture data
without causing flicker on the display.