Type ASSEMBLE
Source Lines : 480
Fixes Applied : 4
Most Recent Version : Wednesday, December 20, 1978
Last Fix ID : [HRC002DS]

Module

     DMSTIO   (TAPEIO)

Function

       TO READ  OR WRITE  A TAPE RECORD  OR TO  CONTROL TAPE
       POSITIONING.

Operation

       DMSTIO FIRST  VERIFIES THAT THE  DEVICE ID  IS VALID.
       IF THE FUNCTION IS A READ, WRITE, READBK, OR SENSE, A
       CONTROL CCW IS BUILT TO SET THE MODE.  IF THE MODE IS
       OMITTED FROM THE PARAMETER LIST, THE MODE IS TAKEN    @VA13323
       FROM THE FIRST BYTE OF THE DEVMISC FIELD OF THE DEVTAB@VA13323
       IN THE NUCLEUS. IF THERE IS NO MODE STORED IN THE     @VA13323
       DEVICE TABLE, THE DEFAULT MODE IS 1600 BPI FOR DUAL   @VA13323
       DENSITY TAPES, ODD PARITY CONVERTER OFF AND           @VA13323
       TRANSLATOR OFF FOR 7-TRACK TAPES.                     @VA13323
       THE BUFFER ADDRESS AND BYTE COUNT ARE FILLED
       INTO A  READ, WRITE, READBK, OR  SENSE CCW AND  IT IS
       COMMAND  CHAINED  TO  THE CONTROL  CCW.   A  DIAGNOSE
       INSTRUCTION IS EXECUTED  TO CAUSE CP TO  INITIATE THE
       I/O  OPERATION.    WHEN  CONTROL  IS   RETURNED,  THE
       OPERATION IS COMPLETE AND  NECESSARY RETRY OPERATIONS
       HAVE ALREADY BEEN EXECUTED BY CP.  IF THE FUNCTION IS
       A CONTROL OPERATION, THE CCW STRING IS BUILT IN THE SAME
       WAY.  A
       DIAGNOSE  INSTRUCTION IS  EXECUTED TO  CAUSE THE  I/O
       OPERATION TO BE  STARTED.  CP WILL RETURN  CONTROL AS
       SOON AS  THE OPERATION IS  STARTED.  CONTROL  IS THEN
       RETURNED TO THE CALLING PROGRAM.

Calls to Other Routines

       NONE