MPC555
/
MPC556
CLOCKS AND POWER CONTROL
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
8-11
Figure 8-6 Divided System Clocks Timing Diagram
The system clocks GCLK1 and GCLK2 frequency is:
Therefore, the complete equation for determining the system clock frequency is:
The clocks GCLK1_50 and GCLK2_50 frequency is:
shows the timing of USIU clocks when DFNH = 1 or DFNL = 0.
GCLK1 Divide by 1
GCLK2 Divide by 1
GCLK1 Divide by 2
GCLK2 Divide by 2
GCLK1 Divide by 4
GCLK2 Divide by 4
FREQ
sys
FREQsysmax
2
DFNH
(
)
or 2
DFNL
1
+
(
)
--------------------------------------------------------
=
where FREQsysmax = System Frequency (FREQ
SYS
)/2
System Frequency (FREQ
SYS
) =
OSCCLK
DIVF + 1
x
(MF + 1)
(2
DFNH
or 2
DFNL + 1
)
2
2
x
FREQ
50
FREQsysmax
2
DFNH
(
)
or 2
DFNL
1
+
(
)
--------------------------------------------------------
1
EBDF
1
+
--------------------------
×
=
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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