Spectracom TPRO-cPCI, User Manual, Page: 14 / 46

Spectracom Corporation TPRO-cPCI/TSAT-cPCI
Synchronizable Timecode Generator User Manual 2-4
There are two methods for using the time code output to drive inputs for multiple boards. The
"T" method connects the output of the master to each slave's input. The advantage of this
method is that, if any board loses the incoming signal, it will report a loss of sync and will not
affect the other slaves; however, it does require an additional connector (usually a BNC "T") at
all but the master and the last slave boards.
The second method is known as a "loop-through.” The output of the master is connected to the
input of the first slave. The output of the first slave is connected to the input of the second
slave, and so on. The advantage is that no additional connectors are needed; but, if the signal
is lost at a given board, all of the boards that are "downstream" from that board will have lost
sync with the master. While they will be in sync with each other (this is usually an advantage),
they can neither recognize nor indicate loss of master sync (a disadvantage).
The user must determine which method is most suitable for the application, although most
applications use the "T" method.
2.9 Time Tag Input
The board latches the on-board clock time into a holding register on the rising edge of this
signal. The user's software is responsible for ensuring that each event is read before the next
occurs.
This is a TTL input with an on-board 10K pull-up resistor to +5V.
2.10 1 PPS Output
This one pulse per second output comes from the on-board clock. It is present regardless of
whether the board is synchronized or freewheeling. An RS-422 driver and series 10-ohm
resistors in each line are on-board. The recommended termination is 120-ohms, ½ watt, line-to-
line (not to ground). The 1PPS Output can be used as a single-ended TTL signal.
2.11 Oscillator Output
Software selects whether this signal is 10 MHz, 5 MHz, 1 MHz, 1 kHz, or Off. It is an RS-422
signal with 10-ohm resistors in each line on the board. The recommended termination is 120-
ohms, ½ watt, line-to-line (not to ground). The driver is enabled (not tri-stated), held in the
"zero" condition, when in the Off mode.
2.12 Heartbeat Output
This is a programmable, periodic pulse with a TTL driver. It is present regardless of whether the
board is synchronized or freewheeling. Power on default state is
off for heartbeat output.
2.13 Match Output
The Match Output is a TTL output. It goes high at a pre-set time and low at another pre-set
time, much like an alarm clock.
2.14 In-Sync Output
This is the same signal that lights the green SYNC light on the front panel and drives the Flag–
Sync bit in the Status Register. It is an open-collector output, suitable for driving an LED or a