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