Spectracom TPRO-cPCI, User Manual, Page: 36 / 46

TPRO-cPCI/TSAT-cPCI Spectracom Corporation
Synchronizable Timecode Generator User Manual 5-6
Other examples:
Desired Pulse Rate Chosen Clock Select N
1.25 MPPS 0x0 (1 * 10
7
) 0xfff8
120 PPS 0x1 (3 * 10
6
) 0x9e58
100 PPS 0x2 (1 * 10
6
) 0xd8f0
0.1 PPS 0x3 (1 * 10
3
) 0xd8f0
Notice that, although 120 PPS and 100 PPS are in the range of clock selects 0x2 and 0x3, the
clock select must be chosen to divide evenly.
5.7 Select Oscillator Output Frequency
0 x 0 n 45
Select the frequency for the Oscillator Output. Write one of the following commands to
tbreg_cmd[3] to specify the frequency. The power-on default is OFF. Read tbreg_response[3]
after sending the command to verify that it has been accepted.
Frequency Command Response
Off 0x00000045 0x????0045
1 kHz 0x00000145 0x????0145
1 MHz 0x00000245 0x????0245
5 MHz 0x00000345 0x????0345
10 MHz 0x00000445 0x????0445
If invalid data is commanded in bits 15:08, the response will be 0x????ff45, and the output will
be OFF.
5.8 Set Offset Time
0 x 0060
This command is used to introduce deliberate offsets into the time. Most applications use the
power-on default (zero delay). Setting a deliberate offset is useful for providing a pre-trigger.
For example, the board's 1PPS output could be used to trigger an instrument at a known time
before an event.
Offset times range from –999 to +999 µS in 1 µS steps. Negative numbers move the board's
time earlier relative to actual time. The offset is coded in BCD format. There is no response.
The board implements the offset by varying the oscillator frequency until the board's time is
changed by the commanded offset. Thus, it may take up to 5 minutes for an offset to take
effect.
Bits tbreg_cmd[0] Bits tbreg_cmd[1]
31:16 (unused) 31:00 (unused)
15:0 N
Bits tbreg_cmd[2] Bits tbreg_cmd[3]
31:00 (unused) 31:16 (unused)
15:00 0x0060