Type ASSEMBLE
Source Lines : 1,803
Fixes Applied : 6
Most Recent Version : Tuesday, December 12, 1978
Last Fix ID : [R15315DS]
Module
DMSXCP ( EXCP ROUTINE )
Function
PROVIDE THE FACILITY TO SIMULATE THE DOS/VS
EXCP (SVC 0) UNDER THE CMS/DOS ENVIRONMENT.
EXCP (EXECUTE CHANNEL PROGRAM) REQUESTS THE
INITIATION OF AN I/O OPERATION TO A SPECIFIC
LOGICAL UNIT.
Attributes
CMSDOS SEGMENT RESIDENT MODULE
REENTRANT
Operation
1. SET UP NECESSARY ADDRESSABILITIES AND SAVE
SOME REGISTERS IN THE EXCP WORK AREA. CHECK
IF THE SPECIFIED CCW ADDRESS IN THE CCB IS
NOT ZERO.
2. DETERMINE IF THE SPECIFIED LOGICAL UNIT IN
THE CCB IS ASSIGNED. IF IT IS ASSIGNED, USE
THE PUB DEVICE TYPE TO INDEX AND BRANCH TO
THE ONE INTERNAL ROUTINE THAT WILL PROCESS
THAT SPECIFIC DEVICE. IF THE LOGICAL UNIT IS
ASSIGNED TO IGNORE, ANOTHER ROUTINE IS GIVEN
CONTROL.
3. LOGICAL UNIT ASSIGNED TO 'IGNORE'.
VERIFY THAT ALL THE CCW'S SPECIFIED ARE VALID.
SEARCH THROUGH CCW CHAIN LOOKING FOR ANY READS.
IF NO READ CCW IS FOUND, THE CCB IS POSTED WITH
THE NORMAL C.E. + D.E. . IF A READ CCW IS FOUND,
ASIDE FROM THE NORMAL C.E. + D.E., THE CCB IS
POSTED FOR EOF.
4. LOGICAL UNIT ASSIGNED TO 'PRINTER'.
A 4 DOUBLE WORD WORK AREA IS ACQUIRED FROM FREE
STORAGE TO BUILD THE DMSPIOSI PLIST. THE PLIST IS
INITIALIZED WITH THE COMMAND NAME AND THE BUFDATA
POINTER. THE FIRST USER CCW IS MOVED TO 'BUFDATA',
AND A NO-OP CCW IS MOVED AFTER IT. IF THE CCW IS
CHAINED, AN INTERNAL FLAG IS SET TO REMEBER THERE
ARE MORE CCW'S TO EXECUTE. IF CCW IS NOT CHAINED,
IT IS CHAINED TO THE NO-OP CCW. AN SVC 202 IS MADE
TO DMSPIOSI TO EXECUTE THIS CCW. UPON RETURN, IF
THERE ARE MORE CCWS, THE OPERATION IS REPEATED AS
BEFORE. OTHERWISE, THE CCB IS POSTED ACCORDINGLY.
5. LOGICAL UNIT ASSIGNED TO 'READER' OR 'PUNCH'.
CHECK IF CCW CODE IS VALID. TURN STACKER SELECT
AND DATA MODE BITS OFF (IF ON) AND PASS CCW CODE
THROUGH TABLE OF SUPPORTED CCWS. ONCE A MATCH IS
FOUND (WILL MATCH ON READ, WRITE, OR NO-OP), THE
PLIST FOR DMSCIO IS BUILT, AND AN SVC 202 IS MADE
TO CARDRD OR CARDPH (READ OR WRITE) TO PERFORM
THE I/O OPERATION. UPON RETURN (OR IF THE CCW IS
TO BE NO-OPED), IF THE CCW IS CHAINED, THE OPERA-
TION IS REPEATED AS BEFORE. OTHERWISE, THE CCB IS
POSTED ACCORDINGLY.
6. LOGICAL UNIT ASSIGNED TO 'TERMINAL'.
CHECK IF CCW CODE IS VALID BY PASSING CCW THROUGH
A TABLE OF SUPPORTED CCWS. ONCE A MATCH IS FOUND
(WILL MATCH ON READ, WRITE, OR NO-OP), THE PLIST
FOR DMSCRD OR DMSCWR IS BUILT. IF READING, A 160
BYTE BUFFER IS ACQUIRED FROM FREE STORAGE TO HOLD
THE INPUT LINE. AN SVC 202 IS ISSUED TO CONREAD OR
TYPLIN TO PERFORM THE I/O OPERATION. UPON RETURN,
IF THE CCW IS CHAINED, THE OPERATION IS REPEATED
AS BEFORE. OTHERWISE, THE CCB IS POSTED ACCORDINGLY.
IF A READ WAS ISSUED, THE NUMBER OF BYTES SPECIFIED
IN THE CCW ARE MOVED TO THE USER'S BUFFER. THEN THE
ACQUIRED FREE STORAGE AREA IS FREED.
7. LOGICAL UNIT ASSIGNED TO 'TAPE'.
THE VIRTUAL DEVICE ADDRESS IS DECODED INTO A HEX
( EBCDIC ) REPRESENTATION FOR ANY POSSIBLE ERROR
MESSAGE SUBSTITUTION.
TWO DUMMY CCWS (MODESET AND TIC) ARE MOVED TO THE
EXCP WORK AREA. A TEST IS MADE TO DETERMINE IF THE
PUB CONTAINS A MODE SET VALUE. IF NOT, THE DEFAULT
VALUE X'B3' IS USED. THE USER CCW CHAIN ADDRESS IS
STORED INTO THE ADDRESS PORTION OF THE TIC CCW AND
A CALL IS MADE TO DIAGNOSE THE CCW CHAIN TO CP.
RETURN IS ONLY MADE IF AN I/O ERROR IS RETURNED BY
CP (EXCLUDING UNIT EXCEPTION OR INCORRECT LENGTH).
IF AN I/O ERROR OCCURED, THE SENSE BYTES ARE TESTED
TO DIFFERENTIATE BETWEEN FILE PROTECTED TAPE OR I/O
ERROR. OTHERWISE, THE CCW IS POSTED ACCORDINGLY.
8. LOGICAL UNIT ASSIGNED TO 'DISK'.
FIRST A CHECK IS MADE TO DETERMINE IF I/O IS TO CMS
FORMATTED DISK, OR TO O/S OR DOS FORMATTED DISK. IF
THE I/O IS TO A CMS FORMATTED DISK, THE CCW IS CHECKED
FOR VALIDITY. IF THE CCW IS 'TIC', THE NEXT CCW IN THE
CHAIN IS PROCESSED. IF THE CCW IS VALID AND NOT 'TIC',
THE CCW IS PASSED THROUGH THE TABLE OF SUPPORTED CCW
CODES. ONCE A MATCH IS FOUND, CONTROL WILL PASS TO THE
ROUTINE TO PROCESS THAT CCW CODE. SUPPORTED CCW CODES
UNDER CMS/DOS ARE: READ DATA, WRITE DATA, SEARCH ID,
WRITE COUNT KEY & DATA, READ COUNT KEY & DATA, READ KEY
AND DATA, AND READ COUNT. ALL OTHER VALID CCWS ARE NO-
OPED. ONCE THE CCW HAS BEEN PROCESSED SUCCESSFULLY, A
CHECK IS MADE TO DETERMINE IF THE CCW IS CHAINED. IF
SO, THE NEXT CCW IS PROCESSED AS BEFORE, OTHERWISE, THE
CCB IS POSTED ACCORDINGLY.
IF THE DISK IS NOT A CMS FORMATTED DISK, A CHECK IS
MADE TO DETERMINE IF THE DISK IS O/S OR DOS FORMATTED.
THE CCW CHAIN IS THEN PASSED THROUGH A TEST TO FIND OUT
IF THERE ARE ANY WRITE CCWS. IF A WRITE CCW IS FOUND,
THE DISK IS CHECKED FOR WRITE MODE. IF THE DISK IS R/O
THE CHANNEL PROGRAM IS NOT EXECUTED. NOW, THE CHANNEL
PROGRAM IS DIAGNOSED TO CP FOR EXECUTION. UPON RETURN
FROM THE CP DIAGNOSE, THE CCB IS POSTED ACCORDINGLY.
Calls to Other Routines
DMSFRE, DMSPIO, DMSCIO, DMSCRD, DMSCWR
DMSBRD, DMSBWR, DMSFNS, DMKGIO, DMSERR