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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)
Содержание MPC8240
Страница 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Страница 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Страница 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Страница 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Страница 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Страница 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Страница 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Страница 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Страница 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Страница 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Страница 516: ...16 14 Watchpoint Trigger Applications ...
Страница 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Страница 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Страница 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...