Intel
®
81341 and 81342—Clocking and Reset
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
986
Order Number: 315037-002US
19.1.1
Clocking Theory of Operation
Each region within the 81341 and 81342 contains different clocking requirements.
These requirements are summarized in the following sections.
19.1.1.1 Clocking Region 1 (PCI Express)
Region 1 obtains its input clock from the PCI Express reference clock The
/-
differential input supplies a 100 MHz clock for normal operation on the PCI Express
interface. The analog front end for this region generates the 2.5 GHz clock used for the
serial PCI Express interface as well as a 250 MHz clock used by the transaction layer. In
addition to the locally generated clocks, region 1 utilizes the internal bus clock
generated by the core PLL to interface to the internal bus (region 3).
Also contains a 25 MHz clock used by the power management logic.
19.1.1.2 Clocking Region 2 (PCI)
Region 2 obtains its input clock from the PCI bus clock connected to the input pin
P_CLKIN
. 81341 and 81342 supports an input frequency of 33 MHz, 66 MHz,
100 MHz, and 133 MHz for normal operation on the PCI interface. Additionally region 2
utilizes the internal bus clock generated by the core PLL to interface to the internal bus
(region 3).