CHAPTER FOUR
4-10
bc635VME/bc350VXI Time and Frequency Processor (Rev. E)
Symmetricom Inc
4.1.7 PACKET “H” SET TIMECODE FORMAT FOR MODE 0
Packet “H” allows the host to select the timecode format and modulation type. The packet
format is as follows. The timecode format and modulation values are maintained in battery
backed RAM.
byte
1
SOH
byte
2
“H”
byte
3
format
byte
4
modulation
byte
5
ETB
Format Choices
“A”
IRIG A
“B”
IRIG B
“C”
2137 (XR3 with 100Hz symbol rate)
“N”
NASA 36
“X”
XR3 (25Hz symbol rate)
Modulation Choices
“M”
amplitude modulated sine wave
Modulated not supported for IRIG A
“D”
pulse code modulation (DC level shift)
DC level shift not is supported for 2137 and XR3 codes.
4.1.8 PACKET “I” CLOCK SOURCE SELECT
Packet “I” is used to select the clock source for the TFP. The TFP uses a frequency of 10MHz
for all timing functions. The 10 MHz be may derived from the TFP VCXO or it may be supplied
from an external oscillator via J1 pin #1 or P2 pin #C22. The packet format is as follows.
byte
1
SOH
byte
2
“I”
byte
3
“E” or “I” External or Internal
byte
4
ETB
On power on the TFP always defaults to the internal oscillator selection. This packet has no
effect on boards with Oven Oscillators
4.1.9 PACKET “J” SEND DATA TO GPS RECEIVER
The format and content variations are discussed in a separate User's Guide.
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