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