Datasheet 113
PCH and System Clocks
4 PCH and System Clocks
PCH provides a complete system clocking solution through Integrated Clocking.
PCH based platforms require several single-ended and differential clocks to synchronize
signal operation and data propagation system-wide between interfaces, and across
clock domains. In Integrated Clock mode, all the system clocks will be provided by PCH
from a 25 MHz crystal generated clock input.
The output signals from PCH are:
• One 100 MHz differential source for BCLK and DMI (PCI Express 2.0 jitter tolerant)
• One 120 MHz differential source for embedded DisplayPort (Mobile Only) on
Integrated Graphics processors.
• Ten 100 MHz differential sources for PCI Express 2.0
• One 100 MHz differential clock for XDP/ITP
• Five 33 MHz single-ended source for PCI/other devices (One of these is reserved as
loopback clock)
• Four flexible single-ended outputs that can be used for 14.31818/24/27/33/48 MHz
for legacy platform functions, discrete graphics devices, external USB controllers,
etc.
4.1 Platform Clocking Requirements
Providing a platform-level clocking solution uses multiple system components
including:
•The PCH
• 25 MHz Crystal source
Table 4-1 shows the system clock input to PCH. Table 4-2 shows system clock outputs
generated by PCH.
NOTES:
1. CLKIN_GND0_[P:N] (Desktop pins only) is NOT used and requires external termination on
Desktop platforms.
2. CLKIN_GND1_[P:N] is NOT used and requires external termination on Mobile and Desktop
platforms.
Table 4-1. PCH Clock Inputs
Clock Domain Frequency Usage description
CLKIN_DMI_P,
CLKIN_DMI_N
100 MHz Unused. External Termination required.
CLKIN_DOT96_P,
CLKIN_DOT96_N
96 MHz Unused. External Termination required.
CLKIN_SATA_P/
CLKIN_SATA_N
100 MHz Unused. External Termination required.
CLKIN_PCILOOPB
ACK
33 MHz
33 MHz clock feedback input to reduce skew between
PCH PCI clock and clock observed by connected PCI
devices. This signal must be connected to one of the
pins in the group CLKOUT_PCI[4:0]
REFCLK14IN 14.31818 MHz Unused. External Termination required.
XTAL25_IN 25 MHz Crystal input source used by PCH.
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