System
Recording series of tests
MGCplus A0534-30.0 HBM: public 269
10.3.2.2 Time channels
The "MGCplus Device Time" time channel (called the "HBM" time channel in
the AB22A) is used to count 76.8 kHz periods. 46 bits are available for the
time count, so it will take 29 years for the counter to overflow.
t
tot
+
2
46
76800
s + 916.259.689, 8133 s + 10.604, 86 d [ 29.05 a
The table below shows the "MGCplus Device Time" format.
Counter 1
Counter 2
Byte 0 Byte 1 Byte 2 Byte 3 Byte 0 Byte 1 Byte 2 Byte 3
8-bit status 23-bit counter + 1 bit sign 8-bit status 23-bit counter + 1 bit sign
Bit no.
0 7 8 3
1
0 7 8
In this format the time begins to be counted after the MGCplus system starts
up with t=0.
The format of the NTP time is an absolute format that contains the system
time of the communication processor. The time information is split between
2 counters of 32 bits each, with one counter containing the number of
seconds since January 1, 1970 00:00:00 UTC and the second counter
counting the s in the current second.
After February 7, 2106 (that is in about 100 years) there will be problems
with the NPT time.
IRIG time channel
This time channel is only available in conjunction with an ML01B on which
special firmware is installed (ML0135BP535.F72). This module is
synchronized to an external IRIG-B source and makes the time information
available in the system. The format of this time channel is identical to NTP
format (see below) with the only difference being that the second
component only contains the seconds of the current year that have passed.
So the channel always overflows with every new year!
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