MPC8378E datasheet(108/127 Pages) FREESCALE

108 / 127 page

MPC8378E PowerQUICC II Pro Processor Hardware Specifications, Rev. 4

108

Freescale Semiconductor

Clocking

22 Clocking

Figure 67 shows the internal distribution of clocks within the MPC8378E.

Figure 67. MPC8378E Clock Subsystem

The primary clock source for the device can be one of two inputs, CLKIN or PCI_CLK, depending on

whether the device is configured in PCI host or PCI agent mode. When the device is configured as a PCI

host device, CLKIN is its primary input clock. CLKIN feeds the PCI clock divider (

÷2) and the

multiplexors for PCI_SYNC_OUT and PCI_CLK_OUT. The CFG_CLKIN_DIV configuration input

selects whether CLKIN or CLKIN/2 is driven out on the PCI_SYNC_OUT signal. The OCCR[PCICOEn]

parameters select whether CFG_CLKIN_DIV is driven out on the PCI_CLK_OUTn signals.

PCI_SYNC_OUT is connected externally to PCI_SYNC_IN to allow the internal clock subsystem to

synchronize to the system PCI clocks. PCI_SYNC_OUT must be connected properly to PCI_SYNC_IN,

with equal delay to all PCI agent devices in the system, to allow the device to function. When the device

is configured as a PCI agent device, PCI_CLK is the primary input clock. When the device is configured

as a PCI agent device the CLKIN signal should be tied to GND.

Core PLL

System PLL

DDR

LBIU

LSYNC_IN

LSYNC_OUT

LCLK[0:2]

MCK[0:5]

core_clk

e300 core

csb_clk to rest

CLKIN

csb_clk

DDR

Memory

Local Bus

PCI_CLK[0:4]

PCI_SYNC_OUT

PCI_CLK/

Clock

Unit

of the device

ddr_clk

lbiu_clk

CFG_CLKIN_DIV

PCI Clock

PCI_SYNC_IN

Device

Memory

Device

to local bus

memory

controller

to DDR

memory

controller

DLL

Clock

Div

Divider

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