Ambassador T8100A, T8102, and T8105
H.100/H.110 Interfaces and Time-Slot Interchangers
Advance Data Sheet
November 1999
2 Architecture and Functional Description (continued)
2.5 Clocking Section (continued)
2.5.8 Clock Control Register Definitions (continued)
Table 50. CKS: Clocks, Secondary (Fallback) Selection, 0x04
Clock register 0x04 is CKS, the secondary clock selection register. This is also referred to as fallback. When pro-
gramming the clock registers, writing to CKW and CKS should be programmed last. The register is defined as fol-
lows.
Reg
R/W
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
CKS
—
FRS
FTS
FF
FCSEL
Symbol
Bit
Description
FRS
7—6 FRS provides an alternate clock resource selection. FRS forces the clock resource selector to
choose a new source for PLL #1.
FRS = 00,
FRS = 01,
FRS = 10,
FRS = 11,
External input (through the 4MHzIN pin).
Resource divider.
DPLL @ 2.048 MHz.
DPLL @ 4.096 MHz.
Note: The decode is the same as that of the CRS bits (in the clock resource register, CKR).
FTS
5—4 FTS determines the basic fallback mode (see Section 2.5.8.1 Basic Fallback Mode).
FTS = 00,
This is automatic fallback to the oscillator divided by 4,
thus 4.096 MHz.
FTS = 01,
FTS = 10,
FTS = 11,
This disables fallback.
This is one of the two major fallback selections.
This fallback selection specifically supports standard H.100 and
H.110 applications.
FF
3
FF forces the use of the FRS, FTS, and FCSEL. FF is used as a test of the fallback, but can
also be used as a software-initiated fallback.
FF = 0,
FF = 1,
Normal operation.
Force use of secondary (fallback) resources.
FCSEL 2—0 FCSEL is used to select an alternate synchronization source. The FCSEL choices are a subset
of the CKSEL values from the CKM register above. The list is presented below:
FCSEL = 000,
FCSEL = 001,
FCSEL = 010,
FCSEL = 011,
FCSEL = 100,
FCSEL = 101—111,
Internal oscillator divided by 4.
NETREF2.
A clocks (C8A & FRAMEA); ECTF or MC-1.
B clocks (C8B & FRAMEB); ECTF or MC-1.
NETREF1.
Selects local references 1—3.
Lucent Technologies Inc.
53
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