Intro 
Curious about PC vs IARE timestamp in spex, and ishell. 
    PC_TIME = ic timestamp before send a message to the iarc system to begin at GO.
  IARC_TIME = DSP toggle a PC parallel port interrupt to timestamp a readout. 
              Parallel port timestamp should be good to about 50 usec, with occcasional 300 usec lags.

Looked at 2019B data from the Legacy archive. Make a list of FITS files, with their PC, and IARC timestamps.


bigdog 
   bigdog.txt - 30613 lines, but 5474 file with no IARC timestamp.
   bigdog2.txt data with the 25139 line with PC and IARC timestamp.

   Output of 'graph.py -f bigdog2.txt':
         size=25138  min=771.0 max=1105.8 mean=774.4 std=2.163
      Graphed n= 25130
      < Range n= 0 : values=  []
      > Range n= 8 :  values= [ 812.262  785.479 1105.786  780.019  842.689  786.374  786.8

   
   


guidedog 

   No data. IARC Timestampe not implemented.

cartman 

   cartman.txt w/ 17457 line with PC and IARC timestamps.

   Output of 'graph.py -f cartman.txt':
      size=17457  min=772.6 max=1959.7 mean=776.2 std=17.041 
      Graphed n= 17315
      < Range n= 0 : values=  []
      > Range n= 142 :  values= [ 811.599  823.484 1027.242  811.781  924.432 1179.506  817.698  815.906
      917.195  972.876  867.061  855.717  873.556  905.722  823.667  870.887 815.382  811.721  833.067  870.313 1010.581  828.638  824.791  823.889
      955.89   823.565  813.508  853.726  876.629  831.792  926.837  811.183 927.94   881.663  823.046  824.705  823.349  824.37   823.408  812.322
      824.691  823.944  824.339  824.038  823.76  1420.018 1129.413 1037.748 829.657  901.585  851.105  866.286  869.317  839.134 1251.259  951.421
      871.013  878.116 1159.344  824.428  812.504  881.046  924.821  824.673 889.225  823.944  822.291  824.277  846.29  1191.226  929.71   842.615
      1273.781  828.452  823.896  823.38   823.649  824.079 1732.948  887.184 994.111  859.845  902.278  826.728  825.822  848.474 1007.42   915.827
      824.135  830.399  822.654  859.54   964.347  888.42   830.09   846.237 820.784  872.533  885.358  883.851  867.162  828.055  820.908  827.504
      1041.607  824.541  873.701  848.776  829.221  830.022  827.667  826.383 943.797  824.459  824.066  823.114  824.007  822.342 1959.742  813.864
      874.732  838.739  825.373  873.99   824.036  817.1    824.097  878.008 812.397  848.503  823.468  874.478  823.945  812.343  824.426  823.21
      825.152  823.954  839.096  824.159  922.665  824.414]

   
   

kyle 

   kyle.txt w/ 14224 lines, but 13291 lines with no IARC timestamp.
   kyle2.txt - 933 lines with PC and IARC timestamp. 

   Output of 'graph.py -f kyle2.txt':
      size=933  min=5.3 max=7.2 mean=6.0 std=0.142 
      Graphed n= 924
      < Range n= 0 : values=  []
      > Range n= 9 :  values= [7.038 7.19  7.02  7.229 7.191 7.048 7.113 7.215 7.001]

   
   


Reference
commands to extract data:
   ./extract-time-data.py --dir /idals/2019B/data/bigdog > bigdog.txt
   grep -v ' 1970-01-01 00' bigdog.txt > bigdog2.txt
   ./extract-time-data2.py --dir /idals/2019B/data/cartman > cartman.txt
   ./extract-time-data2.py --dir /idals/2019B/data/kyle > kyle.txt
   grep -v '0.000000' kyle.txt > kyle2.txt

program used:
extract-time-data.py - python program to extract spex data. 
extract-time-data2.py - modidy program to extract ishell data (slighty differ FIT headers vs spex).
graph.py - python program to statistics and graphs.