mpc8272ec Freescale Semiconductor, Inc, mpc8272ec Datasheet - Page 22

• Manufacturer Part Number: mpc8272ec
• Description: Powerquicc Ii
• Manufacturer: Freescale Semiconductor, Inc

Clock Configuration Modes
Clock Configuration Modes
7
As shown in Table 14, the clocking mode is set according to two sources:
1
2
Within each mode, the configuration of bus, core, PCI, and CPM frequencies is determined by seven bits
during the power-on reset—three hardware configuration pins (MODCK[1–3]) and four bits from hardware
configuration word[28–31] (MODCK_H). Both the PLLs and the dividers are set according to the selected
clock operation mode as described in the following sections.
7.1
Table 15 and Table 16 show configurations for PCI host mode. The frequency values listed are for the
purpose of illustration only. Users must select a mode and input bus frequency so that the resulting
configuration does not exceed the frequency rating of the user’s device. Note that in PCI host mode the input
clock is the bus clock.
22
PCI_HOST_EN
Determines PCI clock frequency range.
PCI_CFG[0]
•
•
PCI_CFG[0]— An input signal. Also defined as “PCI_HOST_EN.” Refer to the Chapter 6,
“External Signals,” and Chapter 9, “PCI Bridge,” in the MPC8272 PowerQUICC II™ Family
Reference Manual.
PCI_MODCK—Bit 27 in the Hard Reset Configuration Word. Refer to Chapter 5, “Reset,” in the
MPC8272 PowerQUICC II™ Family Reference Manual.
0
0
1
1
Clock Configuration Modes
PCI Host Mode
1
Clock configurations change only after PORESET is asserted.
The minimum Tval = 2 when PCI_MODCK = 1, and the minimum
Tval = 1 when PCI_MODCK = 0. Therefore, designers should use clock
configurations that fit this condition to achieve PCI-compliant AC timing.
Pins
PCI_MODCK
MPC8272 PowerQUICC II™ Family Hardware Specifications
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
0
1
0
1
Freescale Semiconductor, Inc.
For More Information On This Product,
Table 14. MPC8272 Clocking Modes
2
NOTE: Tval (Output Hold)
Go to: www.freescale.com
Clocking Mode
PCI agent
PCI host
NOTE
PCI Clock Frequency
Range (MHZ)
50–66
25–50
50–66
25–50
Reference
Table 15
Table 16
Table 17
Table 18
MOTOROLA