Hardware DescriptionBCM5718 Programmer’s Guide
Broadcom®
January 29, 2016 • 5718-PG108-R Page 155
EAV Reference Clock/Counter
The EAV Reference Clock (Count) is a 64-bit free-running clock-tick counter with a 1ns time base. All Real-Time
sensitive services needed by EAV are in reference to this counter. In the 5719/5720 chip, this counter is clocked
by a 125 MHz free running DLL. Therefore, the precision of this counter is limited to 8ns for this generation of
NIC. This implies that the LSB 3-bits of EAV Reference Count shall always be "000" in this chip. This counter
will emerge with a 0 value from Power on Reset and always count upwards. After reaching the full count, the
counter will roll-over to 0 and count up again. These two counters are the only static attributes of this clock. The
rest are programmable.
Time referencing, Time-stamping, Time-sampling etc. all real-time interfacing of the chip hardware with the AV
Device Driver shall be performed in reference to this counter.
The following are the instrumentations available for the EAV Reference Counter:
1. Reset Control: The Driver has the option to configure the EAV Reference Counter to be reset in response to
the following events:
a. GRC Reset (MAC-core soft reset) and PCIE FLR (if supported)
b. PCIe Link Reset
c. Network Link transition from UP→DOWN
d. Network Link transition from DOWN→UP
2. Explicit Driver Controls:
a. Driver may reset the counter.
b. Driver may stop the counter.
c. Driver may re-start the counter after being stopped.
d. Driver may over-write the counter value by PIO write.
3. The driver may read the value of the free-running counter anytime. For that purpose, a 32-bit Register pair
is provided.
4. The driver may take a snap-shot of this counter.
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