For now the Dispatcher\u00a0initialization\u00a0routine will simply add the dummy Wait Task to the TCB queue. \u00a0This dummy task TCB must always be present and must be the first TCB on the queue. \u00a0Because 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. \u00a0Later we will add additional TCB’s that will perform some work.<\/p>\n
000000 4 TXXDINIT CSECT ,\r\n000000 18CF 5 LR R12,R15 ESTABLISH\r\n 00000 6 USING TXXDINIT,R12 BASE REGISTER\r\n 7 *\r\n000002 58B0 0010 00010 8 L R11,16 CVT ADDRESS\r\n 00000 9 USING @CVT,R11\r\n 10 *\r\n000006 4140 C098 00098 11 LA R4,WAITTASK POINT TO DUMMY WAIT TASK\r\n 00000 12 USING @TCB,R4\r\n 13 *\r\n00000A 9640 4004 00004 14 OI TCBFLGS,TCBFNDSP DO NOT DISPATCH TASK\r\n 15 *\r\n00000E 5040 B004 00004 16 ST R4,CVTTASKQ ADD TO TASK QUEUE\r\n000012 5040 B000 00000 17 ST R4,CVTCTCB MAKE IT CURRENT TASK\r\n000088 07FE 51 BR R14 RETURN TO CALLER<\/pre>\nThe only thing we need to do to set up the TCB is to set the Do Not Dispatch flag (TCBFNDSP).<\/p>\n
60 PUSH PRINT\r\n 61 PRINT NOGEN\r\n 62 @TCB ,\r\n 110 @RB ,\r\n 142 POP PRINT\r\n\r\n000094 146 TXXDINIT CSECT ,\r\n000098 147 WAITTASK DS 0D\r\n000098 0000000000000000 148 DC (TCBLEN)X'00'<\/pre>\nBecause 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. \u00a0To do so, we can include the @TCB macro to define the DSECT and then we continue the CSECT.<\/p>\n
[Next – TXXSVCIR – SVC Interrupt Routine<\/a>]<\/p>\n","protected":false},"excerpt":{"rendered":"
For now the Dispatcher\u00a0initialization\u00a0routine will simply add the dummy Wait Task to the TCB queue. \u00a0This dummy task TCB must always be present and must be the first TCB on the queue. \u00a0Because we are not adding any other TCB’s … Continue reading