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AMD Geode™ LX Processors Data Book 557
GeodeLink™ Control Processor Register Descriptions
33234H
6.14.2.14 GLCP Dot Clock PLL Control (GLCP_DOTPLL)
This register does not include hardware handshake controls like the GLCP_SYS_RSTPLL register (MSR 4C000014h), so
care should be taken when changing the settings. For example, to change the DIV settings: write the register with the DOT-
RESET bit (bit 0) set and either in the same write or another write change the DIV settings; read the register until the LOCK
bit (bit 25) goes active (or until a timeout occurs, if desired); write the register with the same DIV settings and with the DOT-
RESET bit clear. The MDIV, NDIV, and PDIV (bits [46:32]) settings work in conjunction to create the internal DOTCLK using
this equation:
For example, with bits [46:32] in the GLCP_DOTPLL register set to 0x00D7 (reset), the Dot clock frequency that the DC and
VP would run with would be:
However, not all MDIV, NDIV, and PDIV settings lock and not all that lock have good long-term jitter characteristics. The PLL
resets to 25.0565 MHz for VGA monitors assuming a 14.31818 MHz input. A 27 MHz input will successfully lock at about 47
MHz, and should then be changed to the desired pixel rate.
Table 6-88. Bootstrap Bit Settings and Reset State of GLCP_SYS_RSTPLL (PW1 and IRQ13 vary)
{PW1,IRQ13,PW0,SUSPA#,GNT#[2:0]}
same as GLCP_SYS_RSTPLL[7:1]
CPU
Speed
CORE
MULT
GLIU
Speed
GLIU
MULT
GLCP_SYS_RSTPLL
Reset Value
0100000 Bypass 11 Bypass 7 00000396_00001840h
1000001 166 4 166 4 00000249_03000082h
1110111 500 14 400 11 000005DD_030000EEh
MSR Address 4C000015h
Typ e R /W
Reset Value 000000D7_02000000h
Fout Fin
NDIV 1+()
MDIV 1+()PDIV 1+()⋅
---------------------------------------------------------------
⋅=
Fout 14.318MHz
13 1+()
01+()71+()
----------------------------------
⋅ 25.0565MHz==
GLCP_DOTPLL Register Map
63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
RSVD
DIV4
RSVD
MDIV NDIV PDIV
313029282726252423222120191817161514131211109876543210
SWFLAGS
LOCK
HALFPIX
RSVD
BYPASS
PD
CAPEN
RSVD RSVD
DOTRESET