MPC8270 MOTOROLA [Motorola, Inc], MPC8270 Datasheet - Page 23

• Manufacturer Part Number: MPC8270
• Description: PowerQUICC II Family Hardware Specifications
• Manufacturer: MOTOROLA [Motorola, Inc]

1
7
The MPC8280 has three clocking modes: local, PCI host, and PCI agent. The clocking mode is set according
to three input pins—PCI_MODE, PCI_CFG[0], PCI_MODCK—as shown in Table 14.
MOTOROLA
PCI_MODE
Determines PCI clock frequency range. Refer to Sections 7.2 and 7.3.
1
0
0
0
0
Clock Configuration Modes
1:2, 1:3, 1:4, 1:5, 1:6
CLKin
CLKin
CLKin
PCI_CFG[0] PCI_MODCK
PLL Clock Ratio
Figure 12 is a representation of the information in Table 13.
The UPM machine outputs change on the internal tick determined by the
memory controller programming; the AC specifications are relative to the
internal tick. Note that SDRAM and GPCM machine outputs change on
CLKin’s rising edge.
Pins
—
0
0
1
1
Figure 12. Internal Tick Spacing for Memory Controller Signals
1:2.5
1:3.5
MPC8280 PowerQUICC II™ Family Hardware Specifications
T1
T1
T1
Table 13. Tick Spacing for Memory Controller Signals
—
T2
0
1
0
1
Table 14. MPC8280 Clocking Modes
T2
T2
1/4 CLKin
3/10 CLKin
4/14 CLKin
Tick Spacing (T1 Occurs at the Rising Edge of CLKin)
1
T3
T3
T3
T2
Clocking Mode
PCI agent
Local bus
PCI host
NOTE
T4
T4
T4
1/2 CLKin
1/2 CLKin
1/2 CLKin
T3
Frequency Range
for 1:2, 1:3, 1:4, 1:5, 1:6
PCI Clock
(MHZ)
50–66
25–50
50–66
25–50
for 1:2.5
for 1:3.5
—
3/4 CLKin
8/10 CLKin
11/14 CLKin
Clock Configuration Modes
T4
Reference
Table 15
Table 16
Table 17
Table 18
Table 19
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