Type ASSEMBLE
Source Lines : 1,729
Fixes Applied : 6
Most Recent Version : Thursday, December 7, 1978
Last Fix ID : [R13548DK]

Module

       DMKVCA

Function

       TO SIMULATE THE CHANNEL AND DEVICE OPERATIONS OF THE
       CHANNEL-TO-CHANNEL ADAPTER (CTCA) CONNECTED BETWEEN TWO
       VIRTUAL MACHINES UNDER VM/370

Attributes

       REENTRANT, PAGEABLE, CALLED VIA SVC

Operation

       DMKVCAST IS CALLED FROM DMKVIOEX AT THE SAME POINT WHERE
       DMKIOSQV IS CALLED FOR NON-SIMULATED DEVICES. AT ENTRY,
       DMKVCAST INITIALIZES THE IOBLOK AS DMKIOSQV WOULD, AND
       THEN TESTS THE VDEVBLOK TO DETERMINE IF THE VIRTUAL CTCA
       IS 'COUPLE'D TO ANOTHER CTCA. IF NOT, DMKDIASM IS CALLED
       TO INTERPRET THE CCW STRING AND SIMULATE THE CORRECT
       CSW AND SENSE STATUS. IF YES, START I/O SIMULATION
       PROCEEDS AS FOLLOWS:

       1.  THE 'CHXBLOK' AND 'CHYBLOK' ARE REFERENCED THRU THE
           X-SIDE AND Y-SIDE VDEVBLOK'S (IN THIS DISCUSSION, THE
           X-SIDE IS ALWAYS THE INITIATING CHANNEL).
       2.  THE FIRST REAL CCW AND THE IOBCAW ARE VALIDATED. IF
           ANY ERRORS ARE DETECTED, A CHANNEL PROGRAM CHECK IS
           GENERATED AND THE SIMULATION TERMINATES VIA STEP ??
       3.  THE REAL CCW STRING PRODUCED BY DMKCCWTR IS INTERPRETED
           ONE CCW AT A TIME BASED ON THE OPERATION TYPE:

       TRANSFER IN CHANNEL:  X'08'
             IF 'TIC' IS FIRST CCW, GENERATE CHANNEL PROGRAM CHK
             IF 'TIC' POINTS TO 'TIC', CAUSE CHANNEL PROGRAM CHK
             OTHERWISE, RESTART WITH NEW CCW STRING.

       SENSE ADAPTER STATE (EXTENDED MODE ONLY):  X'14'
             TEST FOR A PREVIOUS Y-SIDE RESET NOT YET CLEARED
             AND PRESENT INTERVENTION REQUIRED IF YES.
             TEST FOR ATTENTION PENDING FROM Y-SIDE, PRESENT
             'ATTN + BUSY' IN INITIAL STATUS IF YES.
             OTHERWISE, PRESENT SENSE BYTE ZERO.
          IN ALL CASES, SUPPRESS DATA TRANSFER IF 'SKIP' IN CCW.

       SENSE COMMAND BYTE:  X'04'
             EXTENDED MODE:  IF PREVIOUS X-SIDE RESET OR HALT I/O
                HAS NOT BEEN CLEARED, CLEAR RESET CONDITION,
                PRESENT DEVICE END TO Y-SIDE, AND STORE COMMAND
                BYTE OF ZERO.
                IF PREVIOUS Y-SIDE RESET OR HALT I/O HAS NOT BEEN
                CLEARED, PRESENT UNIT CHECK IN INITIAL STATUS.
                IF X-SIDE END-OF-FILE LATCH IS SET, RESET LATCH
                AND STORE COMMAND BYTE OF ZERO.
                OTHERWISE, STORE COMMAND BYTE FROM Y-SIDE ADAPTER
                BLOCK. IF THE Y-SIDE COMMAND WAS A CONTROL, PRESENT
                DEVICE END TO THE Y-SIDE CHANNEL.
             COMPATIBILITY MODE:  STORE COMMAND BYTE FROM Y-SIDE
                ADAPTER BLOCK. IF THE Y-SIDE COMMAND WAS A CONTROL,
                PRESENT DEVICE END TO THE Y-SIDE CHANNEL.
             IN ALL CASES, SUPPRESS DATA TRANSFER IF 'SKIP' IN CCW.

       EXTENDED-MODE ONLY - WRITE, READ CONTROL:
             IF A PREVIOUS X-SIDE HALT I/O OR RESET HAS NOT BEEN
             CLEARED, CLEAR THE CONDITION AND PRESENT DEVICE END
             TO THE Y-SIDE CHANNEL.
             IF A PREVIOUS Y-SIDE HALT I/O OR RESET HAS NOT BEEN
             CLEARED, PRESENT UNIT CHECK IN INITIAL STATUS.
             OTHERWISE, CONTINUE WITH COMMAND PROCESSING.

       CONTROL IMMEDIATE:  X'07'
             RESET THE X-SIDE END-OF-FILE LATCH IF SET.
             IF THE Y-SIDE HAS AN ACTIVE READ, WRITE OR CONTROL
             COMMAND, PRESENT 'ATTN + BUSY'.
             OTHERWISE, PRESENT ATTENTION TO THE Y-SIDE CHANNEL,
             CHANNEL END TO THE X-SIDE CHANNEL, AND WAIT FOR
             A 'SENSE COMMAND BYTE' FROM THE Y-SIDE.

       DISABLE COMPATIBILITY - MODIFIED NO-OP X'C3':
             SET THE INHIBIT COMPATIBILITY LATCH IN THE X-SIDE
             ADAPTER BLOCK, INIDCATE THAT BOTH SIDES OF THE
             ADAPTER ARE IN EXTENDED MODE, ADVANCE TO NEXT CCW.

       ENABLE COMPATIBILITY - MODIFIED NO-OP X'43':
             RESET THE X-SIDE INHIBIT COMPATIBILITY LATCH.
             IF THE Y-SIDE INHIBIT COMPATIBILITY LATCH IS SET,
             LEAVE ADAPTER IN EXTENDED MODE AND ADVANCE TO NEXT
             CCW.  IF THE Y-SIDE LATCH IS NOT SET, FORCE THE
             ADAPTER INTO COMPATIBILITY MODE.

       WRITE: X'01'
             RESET THE X-SIDE END-OF-FILE LATCH IF SET.
             IF THE Y-SIDE HAS AN ACTIVE READ COMMAND, ENTER DATA
             TRANSFER MODE.
             IF THE Y-SIDE HAS AN ACTIVE WRITE OR CONTROL COMMAND,
             PRESENT 'ATTN + BUSY'.
             IF THERE IS NO ACTIVE Y-SIDE COMMAND, PRESENT 'ATTN'
             TO THE Y-SIDE CHANNEL AND WAIT FOR Y-SIDE ACTIVITY.

       WRITE END OF FILE: X'81'  (EXTENDED MODE ONLY)
             RESET THE X-SIDE END-OF-FILE LATCH IF SET.
             IF THE Y-SIDE HAS NO ACTIVE COMMAND, SET THE Y-SIDE
             END-OF-FILE LATCH AND CONTINUE PROCESSING.
             IF THE Y-SIDE HAS AN ACTIVE READ COMMAND, PRESENT
             CHANNEL END, DEVICE END, UNIT EXCEPTION TO THE Y-SIDE.
             IF THE Y-SIDE HAS AN ACTIVE CONTROL OR WRITE COMMAND,
             PRESENT 'ATTN + BUSY' TO THE X-SIDE CHANNEL.

       READ X'02' OR READ BACKWARD X'0C':
             EXTENDED MODE: IF THE X-SIDE END-OF-FILE LATCH IS SET,
                RESET THE LATCH AND PRESENT UNIT EXCEPTION IN
                INITIAL STATUS.
             IF THE Y-SIDE HAS AN ACTIVE WRITE COMMAND, ENTER
             DATA TRANSFER MODE.
             IF THE Y-SIDE HAS AN ACTIVE WRITE OR CONTROL COMMAND,
             PRESENT 'ATTN + BUSY'.
             IF THERE IS NO ACTIVE Y-SIDE COMMAND, PRESENT 'ATTN'
             TO THE Y-SIDE CHANNEL AND WAIT FOR Y-SIDE ACTIVITY.

       WHENEVER IT IS NECESSARY TO WAIT FOR ACTIVITY FROM THE
       Y-SIDE CHANNEL, A CPEXBLOK IS BUILT AND THE ADDRESS STORED
       IN THE CHXBLOK FOR LATER RE-CONNECTION VIA A CALL TO
       DMKSTKCP. ANOTHER CPEXBLOK IS BUILT FOR AN EXIT TO THE
       CALLING ROUTINE WHILE PRESERVING THE ENTRY SAVE-AREA.
       AT APPROPRIATE PLACES DURING COMMAND PROCESSING, A CPEXBLOK
       EXIT FOLLOWED BY A CPEXBLOK RESTART IS TAKEN FOR SEQUENCING
       CONTROL AND TIMING CONSIDERATIONS.

       DATA TRANSFER MODE:

             UPON ENTERING DATA TRANSFER MODE, THE FOLLOWING INIT-
       IALIZATION STEPS ARE TAKEN:
       1.  RESET ANY PENDING ATTENTION INTERRUPTS OR FLAGS ON
           BOTH THE X-SIDE AND Y-SIDE ADAPTERS.
       2.  BUILD A CPEXBLOK FOR THE X-SIDE SUCH THAT BOTH X AND Y
           ADAPTERS ARE IN A SOFTWARE 'WAIT' STATUS.
       3.  PRESENT ZERO INITIAL STATUS TO THE X-SIDE CHANNEL.
       4.  EXCHANGE THE X-SIDE AND Y-SIDE IF NECESSARY SUCH THAT
           THE 'READ' OPERATION IS ALWAYS THE X-SIDE ADAPTER.

       DATA TRANSFER WILL PROCEED UNINTERRUPTIBLY TO COMPLETION,
       IN THE FOLLOWING MANNER:
       1.    EXAMINE THE Y-SIDE (WRITE) CCW TO DETERMINE THE
             MAXIMUM SEGMENT LENGTH FOR DATA TRANSFER.
       2.    EXAMINE THE X-SIDE (READ) CCW TO DETERMINE ITS
             MAXIMUM SEGMENT LENGTH FOR DATA TRANSFER.
       3.    EXAMINE THE 'CAW' PROTECTION KEY FOR THE READ CCW
             AND SIMULATE A PROTECTION CHECK IF IT DOES NOT MATCH
             THE REAL STORAGE KEY OF THE READ AREA.
       4.    COMPARE THE DATA SEGMENT LENGTHS FOR READ AND WRITE.
       5.    IF THE READ COUNT IS GREATER THAN THE WRITE COUNT,
             TRANSFER THE DATA SEGMENT AS SPECIFIED BY THE WRITE
             COUNT, AND UPDATE THE WRITE COUNT BY RESTARTING AT
             STEP 1. AND SKIPPING STEPS 2. AND 3.
       6.    IF THE WRITE COUNT IS GREATER THAN THE READ COUNT,
             TRANSFER THE DATA SEGMENT AS SPECIFIED BY THE READ
             COUNT AND UPDATE THE READ COUNT BY RESTARTING AT STEP
             2.
       7.    IF THE READ COUNT EQUALS THE WRITE COUNT, TRANSFER
             THE DATA SEGMENT AND RESTART AT STEP 1.
       8.    WHEN EITHER THE READ OR WRITE CCW STRING HAS BEEN
             EXHAUSTED, DETERMINE IF INCORRECT LENGTH SHOULD BE
             INDICATED FOR EITHER OR BOTH CHANNELS AND RE-CONNECT
             BOTH SIDES VIA CALLS TO DMKSTKCP.

       THE MAXIMUM DATA SEGMENT LENGTH WHICH MAY BE TRANSFERRED
       IN A SINGLE STEP IS DETERMINED AS FOLLOWS:
       1.    NO MORE THAN 2048 BYTES AT ANY TIME - FOR PROTECTION
             KEY CHECKING.
       2.    NO MORE THAN THE LENGTH OF BUFFER FROM THE STARTING
             ADDRESS TO THE NEAREST 2048-BYTE STORAGE BOUNDARY.
       3.    NO MORE THAN THE TOTAL OR REMAINING CCW DATA COUNT.
       DATA TRANSFER WILL CONTINUE SO LONG AS THERE IS REMAINING
       CCW DATA COUNT OR DATA CHAINED CCW'S. COMMAND CHAINING WILL
       STOP DATA TRANSFER IF THE PREVIOUS CCW COUNT IS EXHAUSTED.

       READ BACKWARD DATA TRANSFER:
             THE READ BACKWARD COMMAND TO A CHANNEL-TO-CHANNEL
             ADAPTER RESULTS IN THE DATA BEING INVERTED ON A
             CHARACTER BASIS., SINCE THE WRITE-ING CHANNEL IS
             SENDING DATA IN FORWARD SEUENCE, BUT THE INDEPENDENT
             READ-ING CHANNEL IS READING IN BACKWARD SEQUENCE.
       DATA INVERSION IS PERFORMED IN THE FOLLOWING MANNER:
       1. IF THE READ BUFFER STARTS AT A 7-BYTE BOUNDARY (I.E. AT
          THE LOW-ORDER BYTE OF A DOUBLE WORD), SKIP TO STEP 3.
       2. MOVE DATA ONE BYTE AT A TIME UNTIL A 7-BYTE BOUNDARY IS
          REACHED, OR THE DATA COUNT IS EXHAUSTED.
       3. LOAD INTO A REGISTER PAIR EIGHT BYTES OF WRITE DATA IN
          INVERTED ORDER, AND MOVE TO READ BUFFER VIA A DOUBLE-
          WORD STORE, UNTIL THE LAST DOUBLE-WORD-ALIGNED DATA HAS
          BEEN MOVED.
       4. MOVE THE REMAINDER OF THE DATA SEGMENT A SINGLE CHARACTER
          AT A TIME UNTIL THE COUNT IS EXHAUSTED.

Calls to Other Routines

       DMKFREE  - TO OBTAIN FREE STORAGE
       DMKFRET  - TO RELEASE FREE STORAGE OBTAINED FROM DMKFREE
       DMKDIBSM - TO SIMULATE STATUS FOR A NOT READY DEVICE  @V407510
       DMKSCNVU - TO LOCATE VDEVBLOK, VCUBLOK, VCHBLOK
       DMKSTKCP - TO STACK CPEXBLOKS FOR DEFERRED EXECUTION
       DMKSTKIO - TO STACK IOBLOKS FOR THE SLIH
       DMKTRDSI - TO TRACE SIO'S AND CCW STRINGS TO VIRTUAL CTCA