Clocks and Power Control
MPC885 PowerQUICC Family Reference Manual, Rev. 2
14-12
Freescale Semiconductor
If SCCR[EBDF]=0, the duty cycle of both GCLK1_50 and GCLK2_50 is 50%. However, if
SCCR[EBDF]=1, the duty cycle of GCLK2_50 is 50%, but the duty cycle of GCLK1_50 is 37.5%, as
shown in
Figure 14-7
.
The low-power frequency dividers described in
Section 14.3.1.1, “Internal General System Clocks
(GCLK1C, GCLK2C, GCLK1, GCLK2),”
also affect the frequency and duty cycle of GCLK1_50,
GCLK2_50, and CLKOUT. For an example of this, see
Figure 14-8
.
Figure 14-8. Memory Controller and External Bus Clocks Timing
Diagram for (CSRC=0 and DFNH=1) or (CSRC=1 and DFNL=0)
The frequency of GCLK1_50 and GCLK2_50 are affected both by the SCCR[DFNH] and SCCR[DFNL]
dividers and by the SCCR[EBDF] divider. Thus, the frequency for GCLKx_50 and CLKOUT is:
CLKOUT is the only externally visible clock, and is equivalent to the internal signal GCLK2_50. While
the DPLL is acquiring lock, the CLKOUT signal does not oscillate and remains in a low state.
GCLK1
GCLK2
GCLK1_50
GCLK2_50
CLKOUT
GCLK1_50
GCLK2_50
(EBDF=00)
(EBDF=00)
(EBDF=01)
(EBDF=01)
CLKOUT
(EBDF=00)
(EBDF=01)
GCLKx_50
f req
divout1
freq
2
DFN H
(
)
or 2
DFN L
1
+
(
)
-----------------------------------------------------------
1
EBDF
1
+
--------------------------
×
=
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...