See (p2,gtt) for Tymnet access via VM's Tymnet base. See (p2,tymnet) for a description of the only program that we now expect to use the TBA key.

The Tymnet base interface is either (_working) or not. {It is an exercise for the student to determine the relationship of this definition to IBM subchannel terminology.} The interface becomes working when an I/O operation with the base begins. The interface becomes not working when the base signals the completion of the operation.

A (_data operation) is either a "write then read", "read", or "reread" operation.

A (_long timeout) is 15 seconds on a real machine and 1 hour on a virtual machine.

The TYMNET base access maintains a flag called (_abort) which is initially off. The abort flag is set to off when a data operation completes.

TBA(0,((1,startseq),(outlength,outdata));==>c,((inlength, indata));) ("write then read").

TBA(1,((1,startseq));==>c,((inlength,indata));) ("read").

TBA(2,((1,startseq));==>c,((inlength,indata));) ("reread").

TBA(3;==>c;) ("terminate read").