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SYSGT.md

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Supplemental documentation for SYSGT% (JSYS 16) and GETAB% (JSYS 10)

The following tables can be accessed to find Chaosnet information:

  • CHSTAT (or .CHSTA for GETAB%) for the Chaosnet status block
  • CHPMXT (or .CHPMX for GETAB%) for the max number of data bytes in a Chaosnet packet
  • MYCHAD (or .MYCHA for GETAB%) for my Chaosnet address

Note that CHPMXT is typically 488 (decimal), and that MYCHAD can also be read using CHANM% (function code .CHNPH).

The CHSTAT table currently contains the following:

Index Description
0 CHAON - non-zero if Chaosnet is enabled
1 Device status
2 MYCHAD - my Chaosnet address
3 Number of packets in from interface
4 Number of packets output to interface
5 Number of transmissions aborted
6 Number lost to busy interface
7 Number of packets with CRC errors before read in
10 Number read out as garbage
11 Number with bad bit count
12 Number of packets ignored for other reasons

Note that for the current implementation using Chaos-over-IP, the only indices which are/can be non-zero are 0 and 2. The other counters (index 3-12) refer to packets in/out/etc of the DTE or Unibus interface, which is not currently used.

The most useful index is thus 0, which you get in AC1 by using SYSGT% with sixbit CHSTAT in AC1, or using GETAB% with .CHSTA (65) in AC1.