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PRELIMINARY
S3C6400X RISC MICROPROCESSOR
SYSTEM CONTROLLER
3-7
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
integer value. For example, if DIV
HCLK
has 1 of CLK_DIV0[8], then DIV
PCLK
must be 1, 3, ... of CLK_DIV0[15:12].
Otherwise, the IP’s on APB bus system cannot transfer data correctly.
JPEG and security sub-system on AHB bus system cannot be running at 133MHz.AHB clocks are independently
generated with DIV
CLKJPEG
and DIV
CLKSECUR
. Therefore, they have same constraints as APB clock, i.e., the
operating frequency ratio must be even number (DIV
CLKJPEG
and DIV
CLKSECUR
must be 1, 3, ... of CLK_DIV0[27:24]
and CLK_DIV0[19:18], respectively).
Table 3-2 shows the recommended clock divider ratio.
Table 3-2. Typical value setting for clock dividers (SFR setting value / output frequency)
APLL MPLL DIV
ARM
DIV
HCLKX2
DIV
HCLK
DIV
PCLK
DIV
CLKJPEG
DIV
CLKSECUR
266MHz
266MHz
0 / 266MHz
0 / 266MHz
1 / 133MHz
3 / 66MHz
3 / 66MHz
3 / 66MHz
400MHz
266MHz
0 / 400MHz
0 / 266MHz
1 / 133MHz
3 / 66MHz
3 / 66MHz
3 / 66MHz
533MHz
266MHz
0 / 533MHz
0 / 266MHz
1 / 133MHz
3 / 66MHz
3 / 66MHz
3 / 66MHz
667MHz
266MHz
0 / 667MHz
0 / 266MHz
1 / 133MHz
3 / 66MHz
3 / 66MHz
3 / 66MHz
The divider for ARM independently uses the output clock of APLL and there is no constraint for clock divider value
as shown in the above table.
Clock ratio change
Clock dividers in Figure 3-2 generate various operating clocks including the system operating clocks, ARMCLK,
HCLKX2, HCLK, and PCLK. Figure 3-6 shows a transition waveform when the cock dividers for the system
operating clocks change the ratio from one to two. As shown the figure, PLL output clock will be slow during ratio
changing period. This period is not fixed and approximately 10~20 clock cycles in typical case.
Figure 3-6. Waveform during system clock ratio is changing.
Therefore, if some IP runs with CLKCAM, CLKMFC, DOUT
MPLL
as shown in Figure 3-2, special care may be
required for this ratio-changing period. Otherwise, IPs may be failed to operate.