mpc8314e Freescale Semiconductor, Inc, mpc8314e Datasheet - Page 92
mpc8314e
Manufacturer Part Number
mpc8314e
Description
Powerquicc Ii Pro Processor Hardware Specifications
Manufacturer
Freescale Semiconductor, Inc
Datasheet
1.MPC8314E.pdf
(106 pages)
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Clocking
The primary clock source can be one of two inputs, SYS_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,
SYS_CLKIN is its primary input clock. SYS_CLKIN feeds the PCI clock divider (÷2) and the
multiplexors for PCI_SYNC_OUT and PCI_CLK_OUT. The CFG_SYS_CLKIN_DIV configuration
input selects whether SYS_CLKIN or SYS_CLKIN/2 is driven out on the PCI_SYNC_OUT signal.
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 SYS_CLKIN signal should be tied to GND.
As shown in
loop (PLL) and the clock unit to create the coherent system bus clock (csb_clk), the internal clock for the
DDR controller (ddr_clk), and the internal clock for the local bus interface unit (lbiu_clk).
The csb_clk frequency is derived from a complex set of factors that can be simplified into the following
equation:
In PCI host mode, PCI_SYNC_IN × (1 + ~ CFG_SYS_CLKIN_DIV) is the SYS_CLKIN frequency.
The csb_clk serves as the clock input to the e300 core. A second PLL inside the e300 core multiplies up
the csb_clk frequency to create the internal clock for the e300 core (core_clk). The system and core PLL
multipliers are selected by the SPMF and COREPLL fields in the reset configuration word low (RCWL)
which is loaded at power-on reset or by one of the hard-coded reset options. See Chapter 4, “Reset,
Clocking, and Initialization,” in the MPC8315E PowerQUICC II Pro Host Processor Reference Manual
for more information on the clock subsystem.
The internal ddr_clk frequency is determined by the following equation:
Note that ddr_clk is not the external memory bus frequency; ddr_clk passes through the DDR clock divider
(÷2) to create the differential DDR memory bus clock outputs (MCK and MCK). However, the data rate
is the same frequency as ddr_clk.
The internal lbiu_clk frequency is determined by the following equation:
Note that lbiu_clk is not the external local bus frequency; lbiu_clk passes through the LBIU clock divider
to create the external local bus clock outputs (LCLK[0:1]). The LBIU clock divider ratio is controlled by
LCCR[CLKDIV].
In addition, some of the internal units may be required to be shut off or operate at lower frequency than
the csb_clk frequency. Those units have a default clock ratio that can be configured by a memory mapped
register after the device comes out of reset.
frequency.
92
csb_clk = {PCI_SYNC_IN × (1 + ~ CFG_SYS_CLKIN_DIV)} × SPMF
ddr_clk = csb_clk × (1 + RCWL[DDRCM])
lbiu_clk = csb_clk × (1 + RCWL[LBIUCM])
Figure
MPC8314E PowerQUICC
60, the primary clock input (frequency) is multiplied up by the system phase-locked
™
II Pro Processor Hardware Specifications, Rev. 0
Table 67
specifies which units have a configurable clock
Freescale Semiconductor