Type ASSEMBLE
Source Lines : 1,018
Fixes Applied : 10
Most Recent Version : Monday, January 22, 1979
Last Fix ID : [R13439DK]

Module

        DMKCCH

Function

        THE CHANNEL CHECK HANDLER FUNCTIONS WITH THE I/O INTERRUPT
        HANDLER TO SCHEDULE A DEVICE DEPENDENT ERROR RECOVERY
        PROCEDURE WHEN A CHANNEL DATA CHECK,A CHANNEL
        CONTROL CHECK,OR AN INTERFACE CONTROL CHECK IS DETECTED.

Operation

        1.CONTROL IS PASSED TO DMKCCH AFTER EITHER A SIO WITH FAILING
         STATUS STORED, OR AN I/O INTERRUPT THAT REFLECTS CHANNEL
        CONTROL CHECK,INTERFACE CONTROL CHECK, OR CHANNEL DATA
        CHECK HAS OCCURED.

        2.IF RDEVBLOK AND IOBLOK EXIST -
        DMKCCH WILL BUILD AN IOERBLOK TO BE USED BY THE DEVICE
        DEPENDENT ERP'S TO DETERMINE IF RECOVERY IS POSSIBLE FOR
        CP INITIATED I/O EVENTS. I/O EVENTS ASSOCIATED WITH A VIRTUAL
        USER THAT RESULT IN A CHANNEL ERROR WILL BE REFLECTED TO
        THAT VIRTUAL MACHINE. THE WILL ENABLE THE VIRTUAL MACHINE
        TO DO ITS OWN RECOVERY FROM CHANNEL CHECKS.

        3 AN EXAMINATION OF THE CHANNEL STATUS WORD AND EXTENDED
        CHANNEL STATUS WORD WILL BE PERFORMED TO DETERMINE IF THE
        CHANNEL HAS BEEN RESET OR IF THE RESET CODES ARE INVALID;
        THE CHANNEL STATUS WORD AND EXTENDED CHANNEL STATUS
        WORD WILL ALSO BE EXAMINED TO SEE IF AN INTERFACE
        HANG-UP (INTERFACE INOPERATIVE) HAS OCCURRED.
        IF ANY OF THESE CONDITIONS IS PRESENT A MESSAGE IS
        SENT TO THE OPERATOR AND A WAIT STATE IS PSW IS LOADED. IF
        THIS IS A 4331/4341 PROCESSOR, THERE WILL NOT BE AN I/O FIXED
        OR EXTENDED LOGOUT FOR A CHANNEL CHECK. THERE WILL BE A
        LIMITED CHANNEL LOGOUT. THERE ALSO WILL NOT BE AN IOEL
        POINTER(LOCATION 173-175).

        4.AN ERROR RECORD WILL BE CONSTRUCTED WHICH WILL CONTAIN THE
        EXTENDED CHANNEL STATUS WORD,THE CHANNEL LOGOUT,AND UP
        TO EIGHT ACTIVE UNITS IN USE AT THE TIME OF ERROR ON THE
        DAMAGED CHANNEL.DMKIOECC WILL USE THIS INFORMATION TO
        BUILD THE CHANNEL CHECK RECORD.

        5 THE DEVICE DEPENDENT ERP'S WILL USE THE SEQUENCE
        CODE AND RETRY CODE PORTION OF THE ECSW IN THE IOERBLOK
        TO DETERMINE CORRECT RETRY SEQUENCES.

Calls to Other Routines

1. DMKIOECC TO RECORD ERROR
2. DMKFREE TO GET STORAGE FOR IOERBLOK AND ERROR RECORD.
3. DMKSCNRU TO GET DEVICE BLOCKS.
4. DMKQCNWT TO WRITE CONSOLE MESSAGES.
5. DMKCVTBH TO CONVERT OPERATOR MESSAGES.
6. DMKFRET TO RETURN ERROR RECORD TO FREE STORAGE
7. DMKSCNRD TO GET REAL DEVICE ADDRESS (CCU)