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EPD Rate Channel Data Processing


Table 3. EPD Rate Channel Packet

Byte #Description
1b0: Update flag (MSB)
    1: new; 0:old
b1, b2: Spin quadrant
    00:A; 01:B; 10:C; 11:D
b3: New spin
    0:same; 1:new
b4: Map ID
    0=MAP1; 1=Map2
b5-b7: Motor position (LSB)
    000:Pos.0;...111:Pos. 7
2, 3, 4Rate Channel 1 (24 bits)
5, 6, 7Rate Channel 1 (24 bits)
8, 9, 10Rate Channel 3 (24 bits)
......
143, 144, 145Rate Channel 48 (24 bits)
146HV Monitor Value
147-151Housekeeping/Status
152-21112 PHA events (20 bits each) and 30 bytes of filler, or
24 PHA events (20 bits each

Once the data is retrieved by the CDS, it must sequentially go through the 24-bit rate channel values and add them to the proper rate channel bins defined in the CDS memory.  The addition algorithm for this may be fairly simple (see Appendix A for more details, but determining which bin to address is not so straightforward. This task will be addressed in section 7.

The motor position, spin quadrant, and motor direction (in the science record status byte), all represent the values present during the quadrant that was just completed.  In other words, the motor and spin parameters match up with the rate channel data that is also present in the data for that minor frame.  One could expect, therefore, that in a minor frame data packet in which the "new spin flag" is set, the spin quadrant will equal "D."

Next: Telemetry Output Buffers in the EPD Memory

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Updated 11/2/04, T. Hunt-Ward
tizby@ftecs.com