Datasheet

MPC8250 Hardware Specifications, Rev. 2
Freescale Semiconductor 23
Clock Configuration Modes
3.2 PCI Mode
The PCI mode is selected according to three input pins, as shown in Table 12. In addition, note the
following:
NOTE: PCI_MODCK
In PCI mode only, PCI_MODCK comes from the LGPL5 pin and
MODCK_H[0–3] comes from {LGPL0, LGPL1, LGPL2, LGPL3}.
NOTE: Tval (Output Hold)
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.
NOTE
Clock configurations change only after POR is asserted.
0111_001 66 MHz 3 200 MHz 2 133 MHz
0111_010 66 MHz 3 200 MHz 2.5 166 MHz
0111_011 66 MHz 3 200 MHz 3 200 MHz
0111_100 66 MHz 3 200 MHz 3.5 233 MHz
0111_101 66 MHz 3 200 MHz 4 266 MHz
0111_110 66 MHz 3 200 MHz 4.5 300 MHz
0111_111 66 MHz 3.5 233 MHz 2 133 MHz
1000_000 66 MHz 3.5 233 MHz 2.5 166 MHz
1000_001 66 MHz 3.5 233 MHz 3 200 MHz
1000_010 66 MHz 3.5 233 MHz 3.5 233 MHz
1000_011 66 MHz 3.5 233 MHz 4 266 MHz
1000_100 66 MHz 3.5 233 MHz 4.5 300 MHz
1
Because of speed dependencies, not all of the possible configurations in Table 14 are applicable.
2
The user should choose the input clock frequency and the multiplication factors such that the frequency of the CPU
is equal to or greater than 133 MHz (150 MHz for extended temperature parts) and the CPM ranges between 66–233
MHz.
3
Input clock frequency is given only for the purpose of reference. User should set MODCK_H–MODCK_L so that the
resulting configuration does not exceed the frequency rating of the user’s part.
Table 14. Clock Configuration Modes
1
(continued)
MODCK_H–MODCK[1–3]
Input Clock
Frequency
2, 3
CPM Multiplication
Factor
2
CPM
Frequency
2
Core Multiplication
Factor
2
Core
Frequency
2