
Agere Systems Inc.
77
Data Sheet
May 2001
and Packet Payload Engine
Ambassador T8110 PCI-Based H.100/H.110 Switch
7 Clock Architecture
(continued)
7.4.1.1 Watchdog Timers
A set of watchdog timers is available for all H1x0, H-MVIP MVIP and SC-bus clocks. No watchdogs are available
for LREF[7:0] directly; however, the LREF inputs may be monitored indirectly via watchdogs on the DPLL1 and
DPLL2 sync inputs, or via the failsafe mechanism; see Section 7.7.2 on page 88. The watchdogs sample the
incoming clocks at 32.768 MHz (derived from the XTAL1 crystal) and monitor for loss of signal, as shown below.
Table 61. Watchdog Timer Description
Watchdog
Signal, Value
Description
H1x0 clock monitors*
CT_C8_A at 8.192 MHz
CT_C8_B at 8.192 MHz
ECTF mode. Checks for CT_C8 rising edge within a
35 ns window of its expected arrival.
CT_C8_A at 4.096 MHz
CT_C8_B at 4.096 MHz
MC1 mode. Monitors for loss of signal (falling edges).
FRAME monitors
/CT_FRAME_A
/CT_FRAME_B
/FR_COMP
Monitors for 8 kHz frequency. Detects frame overflow
(i.e., next frame pulse too late) and frame underflow
(i.e., next frame pulse too early).
NETREF monitors*
CT_NETREF1 at 1.544 MHz
CT_NETREF2 at 1.544 MHz
NETREF is T1 bit clock. Monitors for loss of signal
(rising or falling edges).
CT_NETREF1 at 2.048 MHz
CT_NETREF2 at 2.048 MHz
NETREF is E1 bit clock. Monitors for loss of signal
(rising or falling edges).
CT_NETREF1 at 8 kHz
CT_NETREF2 at 8 kHz
NETREF is 8 kHz frame reference. Monitors for
8 kHz frequency. Detects frame overflow
(i.e., next frame pulse too late) and frame underflow
(i.e., next frame pulse too early).
Compatibility clock monitors
/C16± at 16.384 MHz
/C4 at 4.096 MHz
C2 at 2.048 MHz
SCLK, /SCLKx2 at any of
their defined values.
Gross loss-of-signal detector—clocks are sampled
and normalized to 1.024 MHz. It can take up to
976 ns for these watchdog timers to detect loss of a
compatibility clock.
DPLL1, DPLL2 sync
monitors
Output of MUX selector to the
SYNC input of each
DPLL (8 kHz)
Monitors for 8 kHz frequency. Detects frame overflow
(i.e., next frame pulse too late) and frame underflow
(i.e., next frame pulse too early).
* User selects frequency at which to monitor the CT_C8 clocks via register 0x0010C, watchdog select, C8.
DPLL sync reference is expected to be 8 kHz.