Chapter 2. Signal Descriptions and Clocking
2-37
Clocking
be synchronized to the external memory system clocks in half-clock modes. Also, by
enabling the flipping during half-clock modes, the internal hard_reset to the processor core
is delayed by 2
17
(131072) processor clock cycles. This delay is required to insure that the
clocking has been stabilized inside the MPC8240 after a reset.
Figure 2-4. System Clocking with External PLL
2.3.4 Clocking System Solution Examples
This section describes two example clocking solutions for different system requirements.
For systems where the MPC8240 is the host controller with a minimum number of clock
loads, clock fanout buffers are provided on-chip (shown in Figure 2-5). For systems
requiring more clock fanout or where the MPC8240 is an agent device, external clock
buffers may be used as shown in Figure 2-6.
DLL
PLL
OSC
PLL
Processor Core
Local Memory
66.6, 83.3, 100 MHz
Core Clk
PCI Clocks
20–66 MHz
Peripheral Logic
Clocks
sys_logic_clk
MPC8240
.
.
.
.
.
.
PCI_SYNC_IN
PLL
Low
Skew
Buffer
OSC_IN
SDRAM_SYNC_IN*
*(only required if half-clock ratio)
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...