PRECESSION ELEPHANT 2 Scan Head 2
Data from
the scan
head
Within the 20 position data the actual position of the channel is returned
(possibly only the first 16 bits are valid, the remaining four bits are "0"
then). The last of the 4 extension bits contains the Position Acknowledge
signal of the channel.
The sub frame is concluded by 4 bit (V, U, C, and P).
The following table describes all bit of a sub frame.
Bit Description
0
:
3
PA (Preamble)
For description see above. These bits are differently structured than the others.
4
:
23
Position data in two’s complement representation, 0 is the center position. Bit 4 is
the most significant bit (MSB); bit 23 is the least significant bit (LSB).
24
:
26
bits set to 0
27 bit set to 1
28 V (Validity)
If this bit is set then the pattern should not be analyzed by the receiver.
29 U (sUb code data)
Bit set to 0. The sub code data is not used, but reserved for future application.
30 C (Channel status information)
Bit set to 0. The channel status information is not used, but reserved for future
application.
31 P (Parity)
The preamble is not accounted for.
The number of sub frames depends on the number of channels to be transmitted. For a
scan head with up to 4 channels a frame consists of 4 sub frames. A block consists of
192 frames and begins with the preamble "B". The following figure shows
schematically, how blocks are based on sub frames and bits.
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