T-8110L AGERE [Agere Systems], T-8110L Datasheet - Page 68

• Manufacturer Part Number: T-8110L
• Manufacturer: AGERE [Agere Systems]

Ambassador T8110L H.100/H.110 Switch
6 Clock Architecture
6.7 Clock Circuit Operation—Fallback and Failsafe
6.7.1 Clock Fallback (continued)
6.7.1.3 H-Bus Clock Enable/Disable on Fallback
The previous Ambassador devices allowed a fallback mode (A/B fallback) which automatically allowed an H1x0
bus clock master to detect an error in its own output clock and remove itself from the bus, or a clock slave to detect
an error on its incoming clock and promote itself to clock master. The H-bus clocks include:
!
!
!
Refer to Figure 11 and Table 55. The T8110L allows for this mode of operation in two ways:
Register 0x00109(7:4) = 0100: legacy mode, A/B fallback—when this mode is selected, the fallback triggers
allowed are predefined based on the main input clock selection, and the state machine which controls H-bus clock
enable/disable is activated.
Register 0x00109(7:4) = 1001: nonlegacy mode—when this mode is selected, the fallback trigger enable registers
determine what triggers a fallback, and the state machine which controls H-bus clock enable/disable is activated.
68
A clocks: CT_C8_A, /CT_FRAME_A
B clocks: CT_C8_B, /CT_FRAME_B
C clocks: /C16±, /C4, C2, SCLK, /SCLKx2, /FR_COMP
enters & leaves
Master Output
Enable clock
these states
The T8110
based on
updates,
0x00220
register
Initial
(continued)
Figure 11. T8110L H-Bus Clock Enable States
Diag_ABC
Diag_AB
C_Only
B_Only
A Clocks Fail
A_Only
B Clocks Fail
Diagnostic/Forced Clocking
B_Master
A_Master
B Clocks Fail
A Clocks Fail
Fallback Clocking, assumes
Fallback enabled in CKS register
B Clocks Fail
A Clocks Fail
Diag_ABC = Drives A
Clocks, B Clocks and
Clocks and B Clocks,
C_Only = Drives C
C Clocks, no fallback
no fallback permitted
Diag_AB = Drives A
fallback permitted
Clocks only, no
B_Error
A_Error
(continued)
permitted
Reprogram
A Clocks
Reprogram
B Clocks
B_Error = all clocks shut off,
A_Error = all clocks shut off,
to master and drive C clocks
to master and drive C clocks
B_Master = Drives B & C
Clocks, all clocks shut off
A_Master = Drives A & C
Clocks, all clocks shut off
Clocks, can be promoted
waiting for B clocks to be
Clocks, can be promoted
waiting for A clocks to be
in fallbackcondition
in fallbackcondition
in fallbackcondition
in fallbackcondition
B_Only = Drives B
A_Only = Drives A
reprogrammed
reprogrammed
Agere Systems Inc.
February 2004