Novatech Bitronics M87X Series, Руководство пользователя

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ML0021 August 15, 2018
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Copyright 2018 Bitronics, LLC
such that two devices half a world apart could be synchronized to within fractions of a
second if each is connected to an accurate local time master.
There are several vendors who manufacturer these master time devices and there are
many standardized time synchronization protocols. IRIG-B is one of the more commonly
supported standard time code formats.
5.7.2 Introduction to IRIG Standards
IRIG (InteRange Instrumentation Group) standards consist of a family of serial pulse time
clock standards. These standards were initially developed for use by the U.S. Government
for ballistic missile testing. There are several Time Code Formats within the family such as
A, B, E, G, and H. Each Time Code Format has its own unique bit rate.
There are sub-variations within each Time Code Format that specify the Format
Designation, the Carrier/Resolution, and the Coded Expression formats. All standard IRIG
serial time standards use the IRIG B000 configuration.
The first letter following IRIG specifies the Time Code Format and Rate Designation. The
first number following the letter specifies the Format Designation, the second number
specifies the Carrier/Resolution, and the third number specifies the Coded Expressions.
The M87x’s IRIG interface recognizes and decodes the following standard IRIG formats:
IRIG B000, IRIG B002, and IRIG B003. Additionally, IRIG B120 and IRIG123 formats are
recognized when using the M87x Modulated IRIG-B Converter, part number
M870-MODIRIGBCV, connected to one of the Host module serial ports, P2, P3 or P4.
5.7.2a Time Code Format (Rate Generation)
There are six different IRIG Time Code Formats. The M87x supports Time Code Format
B. Time Code Format B specifies a 100-bit frame and a 1 second time frame (10
milliseconds per bit). The 100 bits consist of:
1 - time reference bit,
7 - BCD bits of seconds information,
7 - BCD bits of minutes information,
6 - BCD bits of hours information,
10 - BCD bits of days information,
27 - optional control bits,
17 - straight binary bits representing seconds of day information
15 - index bits
10 - position identifier bits
5.7.2b Format Designation
There are two IRIG Format Designations:
0 - Pulse Width Coded
1 - Sine Wave, Amplitude Modulated.
The Pulse Width Coded format is essentially the envelope of the Amplitude Modulated
format. The M87x supports the Pulse Width Coded format. The M87x Modulated IRIG-B