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Digital Interface (I/F) Aris Valavanoglou Institut f ü r Weltraumforschung (IWF) PowerPoint Presentation
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Digital Interface (I/F) Aris Valavanoglou Institut f ü r Weltraumforschung (IWF)

Digital Interface (I/F) Aris Valavanoglou Institut f ü r Weltraumforschung (IWF)

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Digital Interface (I/F) Aris Valavanoglou Institut f ü r Weltraumforschung (IWF)

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  1. Digital Interface (I/F) Aris Valavanoglou Institut für Weltraumforschung (IWF) Austrian Academy of Sciences

  2. Command & Data Interface • Based on THEMIS IDPU backplane specification • Serial protocol synchronized to a 2^23 Hz clock (CLK8MHz) • FGE receives its own set of CDI signals • CLK (continuous signal provided by DCB) • 2^23 Hz (CLK8MHz) • 1 Hz (CLK1Hz) • Command (CMD) • FGE returns messages via two telemetry (TLM) signals • TMH (128 Hz vector rate continuously) • TML (4 … 128 Hz per command)

  3. x2: CLK1Hz and CLK8MHz x2: TMH and TML Serial Interface Circuit • Two clock signals • 2^23 Hz (~8.4 MHz) • 1 Hz • One Command Line • Two Telemetry Lines • High Rate (TMH) • 128 vectors/sec • Low Rate (TML) • Command able • 4 vectors/sec • 8 vectors/sec • 16 vectors/sec • 32 vectors/sec • 64 vectors/sec • 128 vectors/sec

  4. Command Interface (F5) • Synchronization by first non-zero (Start) bit after 25 zeros • 24-bits long • 8-bit identifier in the MSB (FGE CMD_ID = $8x) • 16-bit data field in the LSB (CMD_DATA) • Start, Stop and odd Parity bit (calculated without Start bit) • Data transferred MSB first • FGE clocks in the data bits on the falling edge of CLK8MHz • Wrong commands rejected and reported to IDPU via TLMH Command I/F Timing

  5. Commands • List of Commands: Page1/3 • Example:

  6. Commands • List of Commands: Page2/3

  7. Commands • List of Commands: Page3/3

  8. Telemetry Interface • Same format for TMH and TML • 16-bit long message word • Plus Start bit • Message preceded by 17 zeros • End of message indicated by Zero instead of Start bit again • FGE message consists of 3 x 24-bit vectors • Each vector sign extended into 2 x 16 bit words • FGE message length is 6 x 16 words (X-MSW, X-LSW, Y-MSW …) Telemetry I/F Timing

  9. Telemetry Interface (F5) • Extented TLMH Message with Status Information 32 bit message (2 x 16 bits) 8 bit Status 24 bit FGM Data X - Vector X-MSW (16 bits) X-LSW (16 bits) free 24 bit FGM Data Y - Vector free 24 bit FGM Data Z - Vector

  10. Telemetry Interface (F5) • Status Bits

  11. Clock Timing Synchronization • Time Synchronization • Constant delay between data acquisition and data transmission (derived from CLK8MHz) • Time stamping done by IDPU • Start of data acquisition with CLK1Hz (one second) sync

  12. Propagation Delay (F6) 1/223 = 119.2 ns Ch1: CLK EGSE output Ch2: CLK after Line Drivers Ch3: TLM after Line Drivers Ch4: TLM FGM output Measured with 74HCXXX Types and Actel ProASIC 500

  13. Propagation Delay (F6) 2x 54AC240 2x 54AC14 1x RTSX-S Input 1x RTSX-S Output 5x RTSX-S Comb. Cell For one complete loop (DCB– FGM – DCB) worst case:51.9 ns Maximum delay allowed (0.5/223): 59.6 ns