FIFO DATA PACKETS
Symmetricom Inc
bc635VME/350VXI Time and Frequency Processor (Rev. E)
4-5
4.1.3 PACKET “C” COMMAND INPUT
This packet has a single data byte and is used to direct the TPF to take the specific actions below.
byte
1
SOH
byte
2
“C”
byte
3
“1” - “6”
(Definitions Below)
byte
7
ETB
“1”
Not Used
(Warm Start on Early Software Versions)
“2”
Software Reset
vectors TFP CPU to Power on Reset Point
“3”
Jamsynch
Force TFP Minor Time To Zero on the Next 1pps Input
“4”
Not Used
(Jamsynch Lockout On Early Software Versions)
“5”
Buf to RTC
Load Current Time to the Real Time Clock IC
“6”
Variables
Dumps Battery Backed RAM to FIFO (Factory Use Only)
4.1.4 PACKET “D” LOAD D/A CONVERTER
The TFP reference crystal oscillator is voltage controlled using the buffered output of a 16 bit
D/A converter as the controlling voltage. Packet “D” allows the user to directly load a 16 bit
value to the D/A converter. This feature would allow a user to fine tune the TFP time base in the
free running mode. We are not aware of any other use for this packet in normal operation. Since
this voltage is routed out of the TFP via pin 9 on the J1 connector to allow external oscillators to
be disciplined, it would provide a means to devise a frequency control algorithm independent of
the TFP. The format is shown below. (See also bit 3 of the path byte loaded by the “P” packet.)
byte
1
SOH
byte
2
“D”
byte
3
“0” - “F”
bits 12-15
byte
4
“0” - “F”
bits 08-11
byte
5
“0” - “F”
bits 04-07
byte
6
“0” - “F”
bits 01-03
byte
7
ETB
Note:
All data fields must be in ASCII format.
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