Datasheet

Chapter 7. Phase-Locked Loop (PLL) 7-3
PLL Operation
multiplied up as determined by the logic level of the multiplexed D[2:0]/DIVIDE[2:0] pins
during reset to create PCLK.
7.2.3 Reduced-Power Mode
The PCLK can be turned off in a predictable manner to conserve system power. To allow
fast restart of the MCF5407 processor core, the PLL continues to operate at the frequency
configured at reset. PCLK is disabled using the CPU STOP instruction and resumes normal
operation on interrupt, as described in Section 7.2.4, “PLL Control Register (PLLCR).”
7.2.4 PLL Control Register (PLLCR)
The PLL control register (PLLCR), Figure 7-2, provides control over the PLL.
Table 7-2 describes PLLCR bits.
76543210
Field ENBSTOP PLLIPL DISBCLKO —
Reset 0000_0000
R/W R/W
Address MBAR + 0x08
Figure 7-2. PLL Control Register (PLLCR)
Table 7-2. PLLCR Field Descriptions
Bit Name Description
7 ENBSTOP Enable CPU STOP instruction. Must be set for the ColdFire CPU STOP instruction to be
acknowledged. Cleared at reset and must be subsequently set for the processor to enter
low-power modes. Only clocks to the core are turned off because of the CPU STOP instruction.
Internal modules remain clocked and can generate interrupts to restart the ColdFire core.
0 Disable CPU STOP
1 Enable CPU STOP; STOP instruction turns off clocks to the ColdFire core.
6–4 PLLIPL PLL interrupt priority level to wake up from CPU STOP. Determines the minimum level an
interrupt (decoded as an interrupt priority level) must be to waken the PLL. The PLL then turns
clocks back on to the core processor and interrupt exception processing occurs.
000 Any interrupts can wake core
001 Interrupts 2–7
010 Interrupts 3–7
011 Interrupts 4–7
100 Interrupts 5–7
101 Interrupts 6–7
110 Interrupt 7 only
111 No interrupts can wake core. Any reset, including a watchdog reset, can wake the core.
No PLL phase lock time is required.
3 DISBCLKO BCLKO disable. Determines whether BCLKO is driven.
0 BCLKO is driven.
1 BCLKO is three-stated. BCLKO can be reenabled only by a reset.
2–0 — Reserved, should be cleared.