Freescale Semiconductor 56F8122 - Manual (Page 91)

Clock Generation Overview
56F8322 Technical Data, Rev. 10.0
Freescale Semiconductor 91
Preliminary
6.5.10.2 Input/Output Short Address Low (ISAL[21:6])—Bit 15–0
This field represents the lower 16 address bits of the “hard coded” I/O short address.
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, the relaxation oscillator, 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.
The memory, peripheral and core clocks all operate at the same frequency (60MHz max).
6.7 Power-Down Modes
The 56F8322/56F8122 operate in one of three power-down modes, as shown in Table 6-2 .
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.
Refer to the PCE register in Section 6.5.9 and ADC power modes. Power is a function of the system
frequency, which can be controlled through the OCCS.
Table 6-2 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 (IRQA)
3. COP reset
4. External reset
5. Power-on reset