TOPS-10 Monitor Calls Manual Volume 2 AA-K039D ... - Trailing-Edge

MTAPE [OPCODE 072]
22.91 MTAPE [OPCODE 072]
FUNCTION
Passes the monitor a code for an extended set of calls; these calls
perform functions for magnetic tapes and are usually called MTAPEs.
Use FILOP. or TAPOP. to perform magnetic tape functions on extended
I/O channels.
Each defined MTAPE code also has a symbolic name; in this chapter the
MTAPEs are discussed ln alphabetical order by their names. For
example, MTAPE 3 has the name MTEOF.; its function is discussed under
the name MTEOF.
Magtape I/O is described in Chapter 14.
The MTAPEs are:
MTWAT.
MTREW.
MTEOF.
MTSKR.
MTBSR.
MTEOT.
MTUNL.
MTBLK.
MTSKF.
MTBSF.
MTDEC.
MTIND.
MTLTH.
[MTAPE 0]
[MTAPE 1]
[MTAPE 3]
[MTAPE 6]
[MTAPE 7]
[MTAPE 10]
[MTAPE 11]
[MTAPE 13]
[MTAPE 16]
[MTAPE 17]
[MTAPE 100]
[MTAPE 101]
[MTAPE 200]
After your program issues the MTAPE monitor call, the monitor waits
for the magnetic tape to complete any action in progress. The monitor
then clears bits 18-25 of the file status word, initiates the
indicated MTAPE function, and returns control immediately to your
program.
The I/O service routine may be reading several blocks ahead of your
program when performing I/O in buffered mode. The execution of the
MTAPE monitor call affects only the physical position of the magnetic
tape and does not change the data that has already been read into the
buffer. Therefore, when your program issues either an IN, INPUT, OUT,
or OUTPUT call after the MTAPE monitor call, the monitor may not
retrieve the buffer containing the block requested. To guarantee that
the requested block will be in the buffer, your program can set up a
single buffer ring. with a single buffer ring the monitor is
prohibited from reading ahead, and it stops the device after every IN,
INPUT, OUT, or OUTPUT monitor call. Alternatively, your program can
set bit 30 (IO.SYN) in the I/O status word. Setting this bit causes
the monitor to stop the device after each buffer is filled on an IN,
INPUT, OUT, OUTPUT, or FILOP. monitor call. Note that the
FILOP. monitor call provides the functions of the MTAPE calls.
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