78
Agere Systems Inc.
Data Sheet
May 2001
and Packet Payload Engine
Ambassador T8110 PCI-Based H.100/H.110 Switch
7 Clock Architecture
(continued)
7.4.1.2 Frame Center Sampling
Frame center samples are used in order to phase-align the incoming frame reference to the internally generated
frame reference; see Section 7.4.5.1 on page 80. The incoming frame reference signal is sampled with a recov-
ered clock (output of the APLL1 feedback divider) to determine the frame center. Frame center sampling is only rel-
evant when the main clock selection is based on a paired bit clock/frame reference, as follows.
7.4.2 Main and Resource Dividers
Two independently programmable dividers are available to divide down the main clock selection signal. The func-
tion ranges from divide-by-1 (bypass) to divide-by-256.
n
For binary divider values of 1, 2, 4, 8, 16, 32, 64, 128, and 256, the output is 50% duty cycle.
n
For a divider value of 193, the output is almost 50% duty cycle (low-level duration is one clock cycle shorter than
high-level duration).
n
For
all
other divider values, the output is a pulse whose width is one full period of the main clock selection signal.
Output of both dividers is available to the DPLL1 and the APLL1 reference selector. The output of the main divider
is also available at the PRI_REF_OUT chip output.
Both dividers are reset whenever a changeover between X and Y clock register sets is detected; see Section 7.3
on page 76. This allows for immediate loading of the newly activated divider register values.
Table 62. Frame Center Sampling
Frame Signal
Corresponding Bit Clock
Sample Clock
/CT_FRAME_A
/CT_FRAME_B
/FR_COMP
CT_C8_A
CT_C8_B
/C16± (H-
MVIP
)
or /C4 (
MVIP
)
or C2 (
MVIP
)
SCLK or /SCLKx2 (SC-bus)
LREF[0]
LREF[1]
LREF[2]
LREF[3]
Recovered 8.192 MHz, rising edge.
Recovered 8.192 MHz, rising edge.
Recovered 4.096 MHz, falling edge.
/FR_COMP
LREF[4]
LREF[5]
LREF[6]
LREF[7]
Recovered 2.048 MHz, rising edge.
Recovered 2.048 MHz, rising edge.
Recovered 2.048 MHz, rising edge.
Recovered 2.048 MHz, rising edge.
Recovered 2.048 MHz, rising edge.