A-4
MPC106 PCIB/MC User's Manual
MOTOROLA
While the MPC106 is servicing a PCI bus transaction in systems using a 603, if the 603 is
still in a power management mode the 603 will not respond to any snoop cycles. Software
should therefore flush the 603’s L1 cache before allowing the system to enter the nap mode
if the system allows a PCI bus access to wake up the MPC106. However, in systems using
the 604, the 604 can be forced to respond to a snoop cycle if the RUN signal (connected to
the QACK signal from the MPC106) is asserted. This response by the 604 is enabled by
clearing PMCR[NO_604_RUN] to 0. If the MPC106 is configured to allow snoop
responses by the 604, there is no need to flush the L1 cache before the 604 enters the nap
mode.
Before entering the nap mode, QREQ from 603 or HALT from 604 will be sampled active
by the MPC106, which will then respond with a QACK signal when it is ready to nap,
thereby allowing the processor to enter either the nap or sleep mode.
A.1.5 Sleep Mode
Sleep mode provides additional power savings when compared to nap mode. As in nap
mode, both MPC106 and the processor should be configured to enable the sleep mode
(although the processor may optionally be configured for nap mode while the MPC106 is
in sleep mode). While the MPC106 is in sleep mode, no functional units are operating
except the system RAM refresh logic (optional), processor bus request monitoring (through
BR0 or BR1), and NMI signal monitoring. A hard reset, a bus request from BR0, a bus
request from BR1 (in a multiprocessor system with PMCR[BR1_WAKE] set to 1), or
assertion of NMI (with PICR1[MCP_EN] set to 1) will wake the MPC106 from the sleep
mode. The PMCR[PM] bit will always be cleared after the MPC106 is awakened from the
sleep mode.
The PLL and SYSCLK input may be disabled by an external power management controller
(PMC) for additional power savings. The PLL can be disabled by setting the
PLL_CFG[0–3] signals in the PLL bypass mode. Note that SYSCLK must continue for at
least three clock cycles after setting the PLL in bypass mode before SYSCLK can be
disabled. When recovering from sleep mode, the external PMC has to re-enable the PLL
and SYSCLK first, and then wake up the system after 100 microseconds of PLL relock
time.
In sleep mode, the system can retain the system memory content through the use of three
different methods. The first method is the normal CBR refresh which is supported by every
system. The second method is to enable the self-refresh mode of the system memory. This
can be supported only if the system memory is capable of supporting the self-refresh mode.
The third method is supported by the operating system by copying all the system memory
data to a hard disk. In this case, there is no need to continue the memory refresh operation.
The programming options for the three memory retention methods are defined by the
configuration of PMCR[LP_REF_EN] and MCCR1[SREN]. If the LP_REF_EN bit is
cleared to 0, there will be no memory refresh operation when the MPC106 is in the sleep
or suspend mode. If PMCR[LP_REF_EN] is set to 1, memory refresh will be carried out