Clocks and Power Control
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
14-17
bypass capacitors. An inductor value of 8.2 Mhz and bypass capacitor values of 0.1 µF and 10 µF provide
a two-pole filter with a cutoff frequency of 500 Hz.
VSSSYN and VSSSYN1 must have a low-impedance path to the ground plane. If sufficient isolation is
provided for VDDSYN (as described above), no additional isolation for VSSSYN and VSSSYN1 is
required.
14.5
Power Control
To optimize power consumption, the MPC885 provides a low-power mode that can be used to dynamically
activate and deactivate certain internal modules, such that only the needed modules are operating at any
given time. In addition to normal high mode (i.e. fully activated), the MPC885 supports a normal low
mode.
In addition to the normal low power-saving mode, it should be noted that the architecture of the CPM
inherently supports optimum power consumption. When the CPM is idle, it uses its own power-saving
mechanism to shut down automatically.
The normal low power mode is controlled in the PLPRCR[CSRC]. Events can cause automatic changes
from normal low to normal high mode. These events include software-initiation, CPM activity, internal
interrupt sources, external interrupt sources, and resets.
14.5.1
Normal High Mode
Normal high mode is the default mode of the MPC885. In this mode, the GCLKx frequency is determined
by SCCR[DFNH], and all modules of the MPC885 are enabled. For more information about
SCCR[DFNH], refer to
Section 14.3.1.1, “Internal General System Clocks (GCLK1C, GCLK2C, GCLK1,
GCLK2).”
Normal high mode is selected if PLPRCR[CSRC]=0 and PLPRCR[LPM]=00, or if an enabled event has
caused an exit from Normal Low power mode.
14.5.2
Normal Low Mode
Normal low mode takes advantage of the low-power dividers for GCLKx to enable full functionality of
the MPC885, but at a lower frequency so that power consumption is reduced. The low-power dividers
allow the system to reduce and restore the operating frequencies of different sections of the MPC885
without losing the DPLL lock. This mode is sometimes called slow-go or low gear mode.
Normal low mode is selected if PLPRCR[CSRC]=1. In normal low mode, the GCLKx frequency is
determined by SCCR[DFNL]. For more information about SCCR[DFNL], see
Section 14.3.1.1, “Internal
General System Clocks (GCLK1C, GCLK2C, GCLK1, GCLK2).”
Normal low mode can be entered at any time, and the frequency of operation of normal low mode can be
changed dynamically. This is controlled by PLPRCR[CSRC] and SCCR[DFNL]. Changes to these bits
take effect immediately.
Содержание PowerQUICC MPC870
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Страница 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Страница 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Страница 192: ...MPC885 Instruction Set MPC885 PowerQUICC Family Reference Manual Rev 2 5 22 Freescale Semiconductor ...
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Страница 416: ...External Bus Interface MPC885 PowerQUICC Family Reference Manual Rev 2 13 42 Freescale Semiconductor ...
Страница 440: ...Clocks and Power Control MPC885 PowerQUICC Family Reference Manual Rev 2 14 24 Freescale Semiconductor ...
Страница 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Страница 606: ...SDMA Channels and IDMA Emulation MPC885 PowerQUICC Family Reference Manual Rev 2 19 20 Freescale Semiconductor ...
Страница 738: ...SCC Asynchronous HDLC Mode and IrDA MPC885 PowerQUICC Family Reference Manual Rev 2 25 16 Freescale Semiconductor ...
Страница 780: ...SCC Ethernet Mode MPC885 PowerQUICC Family Reference Manual Rev 2 27 24 Freescale Semiconductor ...
Страница 794: ...SCC Transparent Mode MPC885 PowerQUICC Family Reference Manual Rev 2 28 14 Freescale Semiconductor ...
Страница 848: ...Serial Peripheral Interface SPI MPC885 PowerQUICC Family Reference Manual Rev 2 30 18 Freescale Semiconductor ...
Страница 882: ...Universal Serial Bus USB MPC885 PowerQUICC Family Reference Manual Rev 2 31 34 Freescale Semiconductor ...
Страница 944: ...Parallel I O Ports MPC885 PowerQUICC Family Reference Manual Rev 2 34 26 Freescale Semiconductor ...
Страница 956: ...CPM Interrupt Controller MPC885 PowerQUICC Family Reference Manual Rev 2 35 12 Freescale Semiconductor ...
Страница 1004: ...Buffer Descriptors and Connection Tables MPC885 PowerQUICC Family Reference Manual Rev 2 37 30 Freescale Semiconductor ...
Страница 1022: ...ATM Parameter RAM MPC885 PowerQUICC Family Reference Manual Rev 2 38 18 Freescale Semiconductor ...
Страница 1068: ...ATM Pace Control MPC885 PowerQUICC Family Reference Manual Rev 2 40 22 Freescale Semiconductor ...
Страница 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Страница 1120: ...AAL2 Implementation MPC885 PowerQUICC Family Reference Manual Rev 2 44 30 Freescale Semiconductor ...
Страница 1162: ...Fast Ethernet Controller FEC MPC885 PowerQUICC Family Reference Manual Rev 2 45 40 Freescale Semiconductor ...
Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Страница 1313: ...MPC885 PowerQUICC Family Reference Manual Rev 2 Freescale Semiconductor B 1 Appendix B Serial Communications Performance TBD ...
Страница 1314: ...Serial Communications Performance MPC885 PowerQUICC Family Reference Manual Rev 2 B 2 Freescale Semiconductor ...
Страница 1320: ...Register Quick Reference Guide MPC885 PowerQUICC Family Reference Manual Rev 2 C 6 Freescale Semiconductor ...
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Страница 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Страница 1384: ...Serial ATM Scrambling Reception and SI Programming MPC885 PowerQUICC Family Reference Manual Rev 2 H 6 Freescale Semiconductor ...
Страница 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...