30 097-55501-01 Issue 6 – June 2003
1
TimeHub 5500 System Guide
operation.
There are several restrictions and special considerations that apply to
Passthrough operation:
• There are likely to be brief phase hits on the outputs when entering
and exiting Passthrough mode
• No configuration of clock or outputs is possible while in
Passthrough mode
• Passthrough input qualification is as described previously. It does
not have the capability to reject inputs with excessive jitter or that
are significantly off frequency.
• Passthrough does not filter input-to-output in the same way as a
clock card, so out-of-mask timing (for example, TDEV and MTIE) is
possible.
To check firmware or hardware revision numbers, use the RTRV-NETYPE-
ALL command as shown below.
• For firmware revision numbers, a higher numeric value indicates a
later (newer) revision. For example, 4315B is newer than 4312A
because 4315 is larger than 4312. Firmware version information
always appears in the second comma-separated field after the
product number information.
• For hardware revisions, later occurring letters indicate newer
revisions (revision B is newer than revision A). The hardware
revision information is appended to the product number
information. For example, 090-55542-01-B indicates model
number 090-55542-01 having hardware revision B. In cases where
there is no hardware version indicated (just a product number), it
means the hardware revision is A.
As an example, sending
RTRV-NETYPE-ALL:::SV73;
Produced the following response on a TimeHub shelf (entire response not
shown):
N
OTE
: Since Passthrough is not a normal operating mode, it
should not be routinely used. It is intended to provide a
mechanism to “keep alive” the outputs in a situation where both
clock cards are inadvertently removed. The timing performance
when in Passthrough mode cannot be assured.
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