FIFO DATA PACKETS
Symmetricom Inc
bc635VME/350VXI Time and Frequency Processor (Rev. E)
4-15
4.1.14 PACKET “P” PATH SELECTION
The path selection might better be called a switch or branch selector. The purpose of this packet
is to allow the user to exercise control over certain TFP processes. The path packet is used to
download a single byte. Each bit in the byte has a toggling action relative to a TFP function.
The format is described below.
byte
1
SOH
byte
2
“P”
byte
3
“0” - “F” path upper nibble
byte
4
“0” - “F” path lower nibble
byte
5
ETB
Upper Nibble Bit Definitions
bit
3
0 = normal time format
1 = long second format (See Note.)
bit
2
0 = no broadcast of RTC
1 = broadcast packet “o” “0” each second
bit
1
0 = use GPS leap seconds
1 = ignore GPS leap seconds
bit
0
0 = FIFO echo off
1 = FIFO
echo on
Lower Nibble Definitions
bit
3
0 = enable TFP disciplining 1 = disable TFP discipline
bit
2
0 = enable jamsynch
1 = disable jamsynch
bit
1
0 = leap year off
1 = leap year on
bit
0
0 = Accept Day 000
1 = Day 000 invalid (default setting)
Note
: Time
∅
through TIME4 contain atomic seconds since January 6, 1980. Use only in GPS
Mode. (See Table 4-2.)
4.1.14.1 LOWER NIBBLE BIT DESCRIPTIONS
Bit 0
In Time Code mode (Mode 0) it is sometimes desired to use day 000. This is an invalid code in
IRIG time codes and clearing this bit overrides the normal checking and allows a board lock on
this otherwise invalid code. See Chapter Three for a description of the TIME fields (offset
0x0C).
Note
: Day 001 is always January 1 as per IRIG specifications. We allow day 000 only for
those people that want this capability, say for testing purposes (many time-code
generators start with Day 000), and are not bothered by an extra day in the year roll over.
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