Data Format Meinberg Slotcards

Format of the Date and Time Structure

The data structure described here is used to read information on date, time, and status from Meinberg radio clocks in PC slot card format. Additionally, the structure is part of the IPX packets which are used by Meinberg software to synchronize computers in IPX networks. The structure contains 11 bytes (index 0 through 10) which can be read in the following order:

Byte	Contents	Valid Range
0	hundredths of seconds	0..99
1	seconds	0..59, 60 if leap second
2	minutes	0..59
3	hours	0..59
4	day of month	1..31
5	day of week	1..7, 1 for Monday
6	month	1..12
7	year without century	0..99
8	status	coded bit-wise
9	signal strength	0..255
10	offset from UTC [hours]	-128..+127

The status byte is coded bit-wise. Each of the bits represents a piece of information on the radio clock status or the time status. Bit D0 is the least significant bit (LSB) of the status byte:

The status bits are set to 1 under the following conditions:

Bit	if set to 1:
D0	Radio clock (DCF77): The radio clock currently runs on XTAL Radio clock (GPS): The receiver has not yet verified its possition
D1	Time: Daylight saving in effect Unless the UTC status bit is set, the time contained in the data structure represents local daylight saving time.
D2	Radio clock: Has synchronized after last reset
D3	Time: Announcement of start or end of daylight saving time
D4	Time: UTC
D5	Time: Announcement of leap second
D6	Radio clock: Time has been modified via interface
D7	Radio clock: Time is invalid

Notes:

Radio clock: (depending on DCF77 or GPS)
DCF77 receiver: The radio clock currently runs on XTAL
GPS receiver: has not yet verified its possition

Time: Daylight saving in effect.
Unless the UTC status bit is set, the time contained in the data structure represents local daylight saving time.

Radio clock: Has synchronized after last reset.
The radio clock has synchronized at least once after the last reset. Most of the Meinberg time adjustment programs wait until this bit is set before they start adjusting the computer's system time. However, those programs can also be configured to ignore this status bit and do the adjustment immediately.

Time: Announcement of start or end of daylight saving time.
This bit is set during the last hour before local time switches from or to daylight saving. This bit may not be included in IPX packets since this information can not be derived from the computer's operating systems.

Time: UTC.
This bit is always set if the time read from the radio clock is UTC rather than local time. UTC never switches to daylight saving time.

Time: Announcement of leap second.
The time when a leap second must be introduced is determined by the International Earth Rotation Service (IERS). That information is usually broadcasted by time transmitters. Analoguous to the DCF77 Coding Scheme this bit is set during the last hour before the leap second is inserted.

Radio clock: Time has been modified via interface.
The radio clock's time has not been set from DCF77 or the GPS satellites but has been modified via the clock's interface.

Radio clock: Time is invalid.
The time read from the radio clock's real time clock after power-up is invalid. This may happen if e.g. the radio clock's backup battery is discharged. In the IPX broadcast packets this bit may also be set if the radio clock connected to the transmitting computer fails.