9-2
MCF5282 User’s Manual
MOTOROLA
Low-power Mode Operation
9.2.2
1:1 PLL Mode
In 1:1 PLL mode, the PLL synthesizes a frequency equal to the external clock input
reference frequency. The post divider is not active.
9.2.3
External Clock Mode
In external clock mode, the PLL is bypassed, and the external clock is applied to EXTAL.
The resulting operating frequency is equal to the external clock frequency.
9.3
Low-power Mode Operation
This subsection describes the operation of the clock module in low-power and halted modes
of operation. Low-power modes are described in Chapter 7, “Power Management.”
Table 9-1 shows the clock module operation in low-power modes.
Table 9-1. Clock Module Operation in Low-power Modes
During wakeup from a low-power mode, the Flash clock always clocks through at least 16
cycles before the CPU clocks are enabled. This allows the Flash module time to recover
from the low-power mode, and software can immediately resume fetching instructions
from memory.
In wait and doze modes, the system clocks to the peripherals are enabled, and the clocks to
the CPU, Flash, and SRAM are stopped. Each module can disable its clock locally at the
module level.
In stop mode, all system clocks are disabled. There are several options for enabling or
disabling the PLL or crystal oscillator in stop mode, compromising between stop mode
current and wakeup recovery time. The PLL can be disabled in stop mode, but requires a
wakeup period before it can relock. The oscillator can also be disabled during stop mode,
but requires a wakeup period to restart.
When the PLL is enabled in stop mode (STPMD[1:0]), the external CLKOUT signal can
support systems using CLKOUT as the clock source.
Low-power Mode
Clock Operation
Mode Exit
Wait
Clocks sent to peripheral modules only
Exit not caused by clock module, but normal
clocking resumes upon mode exit
Doze
Clocks sent to peripheral modules only
Exit not caused by clock module, but normal
clocking resumes upon mode exit
Stop
All system clocks disabled
Exit not caused by clock module, but clock
sources are re-enabled and normal clocking
resumes upon mode exit
Halted
Normal
Exit not caused by clock module
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...