Datasheet

Clock Generation Overview
56F8365 Technical Data, Rev. 9
Freescale Semiconductor 127
• 0 = The clock is not provided to the peripheral (the peripheral is disabled)
6.6 Clock Generation Overview
The SIM uses an internal master clock from the OCCS (CLKGEN) module to produce the peripheral and
system (core and memory) clocks. The maximum master clock frequency is 120MHz. Peripheral and
system clocks are generated at half the master clock frequency and therefore at a maximum 60MHz. The
SIM provides power modes (Stop, Wait) and clock enables (SIM_PCE register, CLK_DIS, ONCE_EBL)
to control which clocks are in operation. The OCCS, power modes, and clock enables provide a flexible
means to manage power consumption.
Power utilization can be minimized in several ways. In the OCCS, crystal oscillator, and PLL may be shut
down when not in use. When the PLL is in use, its prescaler and postscaler can be used to limit PLL and
master clock frequency. Power modes permit system and/or peripheral clocks to be disabled when unused.
Clock enables provide the means to disable individual clocks. Some peripherals provide further controls
to disable unused subfunctions. Refer to Part 3 On-Chip Clock Synthesis (OCCS), and the 56F8300
Peripheral User Manual for further details.
6.7 Power-Down Modes Overview
The 56F8365/56F8165 operates in one of three power-down modes, as shown in Table 6-4.
All peripherals, except the COP/watchdog timer, run off the IPbus clock frequency, which is the same as
the main processor frequency in this architecture. The maximum frequency of operation is
SYS_CLK = 60MHz.
Table 6-4 Clock Operation in Power-Down Modes
Mode Core Clocks Peripheral Clocks Description
Run Active Active Device is fully functional
Wait Core and memory
clocks disabled
Active Peripherals are active and can produce interrupts if
they have not been masked off.
Interrupts will cause the core to come out of its
suspended state and resume normal operation.
Typically used for power-conscious applications.
Stop System clocks continue to be generated in
the SIM, but most are gated prior to
reaching memory, core and peripherals.
The only possible recoveries from Stop mode are:
1. CAN traffic (1st message will be lost)
2. Non-clocked interrupts
3. COP reset
4. External reset
5. Power-on reset