Type ASSEMBLE
Source Lines : 139
Fixes Applied : 0
Most Recent Version : Thursday, December 7, 1978
Last Fix ID : [Unmodified]

Module

       DMTSVC

Function

        THE  DMTSVC  MODULE  IS  THE  MSUP  SVC  INTERRUPT
        HANDLER. DMTSVC  RECEIVES CONTROL  DIRECTLY ON  AN
        SVC INTERRUPT.

Attributes

       REUSABLE, EXECUTABLE DISABLED ONLY

Operation

        THE ONLY FUNCTION OF SVC WITHIN THE RSCS SYSTEM IS
        TO "UNDISPATCH"  (OR "FREEZE") AN  EXECUTING TASK.
        SVC IS  NECESSARY TO  PERFORM THIS  FUNCTION SINCE
        THE LEFT HALF OF THE ACTIVE PSW IS ACCESSABLE ONLY
        THROUGH STORAGE  OF THE PSW  ON AN  INTERRUPT. THE
        SVC  CODE  IS  NOT INSPECTED  BY  SUPEXT,  AND  IT
        CURRENTLY HAS NO MEANING (SEE BELOW).

        THE RUNNING  TASK IS "UNDISPATCHED"  ON AN  SVC BY
        MOVING THE  LEFT HALF  OF THE SVC  OLD PSW  TO THE
        TASK  SAVE  AREA  RESUME PSW  FIELD,  STORING  THE
        REGISTER CONTENTS  ON INTERRUPT  IN THE  TASK SAVE
        AREA, AND SETTING THE RESUME  PSW ADDRESS FIELD TO
        THE  CONTENTS  OF  REG.14   ON  INTERRUPT.  SUPSVC
        RETURNS CONTROL  BY SETTING REG.14 TO  THE ADDRESS
        OF THE  TASK ELEMENT  OF THE  "UNDISPATCHED" TASK,
        AND  LOADING A  PSW  WITH ALL  MASK  BITS SET  OFF
        (EXCEPT MACHINE  CHECK) AND  EXECUTION ADDRESS  AS
        STORED IN THE SVC OLD PSW.

Calls to Other Routines

       NONE