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Tsi106 PowerPC Host Bridge Hardware Specifications Manual
80C1000_MA002_02
System Design Information
1.8 System Design Information
This section provides electrical and thermal design recommendations for successful application of the
Tsi106.
1.8.1 PLL Configuration
The Tsi106 requires a single system clock input, SYSCLK. The SYSCLK frequency dictates the frequency
of operation for the PCI bus. An internal PLL on the Tsi106 generates a master clock that is used for all of
the internal (core) logic. The master clock provides the core frequency reference and is phase-locked to the
SYSCLK input. The 60x processor, L2 cache, and memory interfaces operate at the core frequency. In the
5:2 clock mode (Rev. 4.0 only), the Tsi106 needs to sample the 60x bus clock (on the LBCLAIM
configuration input) to resolve clock phasing with the PCI bus clock (SYSCLK).
The PLL is configured by the PLL[0–3] signals. For a given SYSCLK (PCI bus) frequency, the clock
mode configuration signals (PLL[0–3]) set the core frequency (and the frequency of the VCO controlling
the PLL lock). The supported core and VCO frequencies and the corresponding PLL[0–3] settings are
Table 11. PLL Configuration
PLL[0–3]1
Core/SYSCLK
Ratio
VCO
Multiplier
Core Frequency (VCO Frequency) in MHz
PCI Bus
16.6 MHz
PCI Bus
20 MHz
PCI Bus
25 MHz
PCI Bus
33.3 MHz
0001
1:1
x4
—
33.3 (133)
0100
2:1
x2
—
66.6 (133)
0101
2:1
x4
33.3 (133)
40 (160)
50 (200)
—
0110
5:2 2
x2
—
83.3 (166)
0111
5:2 2
x4
41.6 (166)
—
1000
3:1
x2
—
60(120)
75 (150)
—
0011
PLL-bypass 3
PLL off
SYSCLK clocks core circuitry directly
1x core/SYSCLK ratio implied
1111
Clock off 4
PLL off
no core clocking occurs
Notes:
1
PLL[0–3] settings not listed are reserved. Some PLL configurations may select bus, CPU, or VCO frequencies which are
frequencies.
2
5:2 clock modes are only supported by Tsi106 Rev 4.0; earlier revisions do not support 5:2 clock modes. The 5:2 modes
require a 60x bus clock applied to the 60x clock phase (LBCLAIM) configuration input signal during power-on reset,
hard reset, and coming out of sleep and suspend power-saving modes.
3
In PLL-bypass mode, the SYSCLK input signal clocks the internal circuitry directly, the PLL is disabled, and the
core/SYSCLK ratio is set for 1:1 mode operation. This mode is intended for factory use and third-party tool vendors only.
Note also: The AC timing specifications given in this document do not apply in PLL-bypass mode.
4
In clock-off mode, no clocking occurs inside the Tsi106 regardless of the SYSCLK input.