For now the Dispatcher initialization routine will simply add the dummy Wait Task to the TCB queue. This dummy task TCB must always be present and must be the first TCB on the queue. Because we are not adding any other TCB’s to the queue for now the only thing that will happen when we IPL is the Dispatcher will enter the enabled wait until the Interval Timer expires at which time the Dispatcher will once again enter the enabled wait. Later we will add additional TCB’s that will perform some work.
000000 4 TXXDINIT CSECT ,
000000 18CF 5 LR R12,R15 ESTABLISH
00000 6 USING TXXDINIT,R12 BASE REGISTER
7 *
000002 58B0 0010 00010 8 L R11,16 CVT ADDRESS
00000 9 USING @CVT,R11
10 *
000006 4140 C098 00098 11 LA R4,WAITTASK POINT TO DUMMY WAIT TASK
00000 12 USING @TCB,R4
13 *
00000A 9640 4004 00004 14 OI TCBFLGS,TCBFNDSP DO NOT DISPATCH TASK
15 *
00000E 5040 B004 00004 16 ST R4,CVTTASKQ ADD TO TASK QUEUE
000012 5040 B000 00000 17 ST R4,CVTCTCB MAKE IT CURRENT TASK
000088 07FE 51 BR R14 RETURN TO CALLER
The only thing we need to do to set up the TCB is to set the Do Not Dispatch flag (TCBFNDSP).
60 PUSH PRINT
61 PRINT NOGEN
62 @TCB ,
110 @RB ,
142 POP PRINT
000094 146 TXXDINIT CSECT ,
000098 147 WAITTASK DS 0D
000098 0000000000000000 148 DC (TCBLEN)X'00'
Because we want to refer the length of the TCB control block DSECT to define the Wait Task TCB storage, the equate for TCBLEN must be defined before it is used. To do so, we can include the @TCB macro to define the DSECT and then we continue the CSECT.
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