Commodore 128 Programmer's Reference Manual page 439

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I !
THE COMMODORE 128 OPERATING SYSTEM 429
RESULTS:
Registers: .A = error code (if any)
P .X used
J .Y used
Memory: logical tables updated
H STATUS, RSSTAT updated
i I Flags: .C = 1 -> error
j-j EXAMPLE:
' ; LDA#1 ;la
JSR $FFC3 ;CLOSE
H BCS error ;(tape files only)
/ i
CLOSE removes the logical file (LA) passed in .A from the logical file tables
P and performs device-specific closing tasks. Keyboard, screen and any unOPENed
I files pass through. Cassette files opened for output are closed by writing the last
buffer and (optionally) an EOT mark. RS-232 I/O devices are reset, losing any
n buffered data. Serial files are closed by transmitting a CLOSE command (if an SA
was given when it was opened), sending any buffered character, and UNLSTNing
the bus.
„ There is a special provision incorporated into the CLOSE routine of systems
j ! featuring a BASIC DOS command. If the following conditions are all true, a full
CLOSE is not performed; the table entry is removed but a CLOSE command is not
transmitted to the device. This allows the disk command channel to be properly
| OPENed and CLOSEd without the disk operating system closing all files on its
( end:
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.c
FA
SA
= 1
> = 8
= 15
-* indicates special CLOSE
-*■ device is a disk
—» command channel
The path to CLOSE is through an indirect RAM vector at $31C. Applications
may therefore provide their own CLOSE procedures or supplement the system's by
redirecting this vector to their own routine.
24. $FFC6 CHKIN ;set input channel
PREPARATION:
Registers: .X = LA (logical #)
Memory: system map
Flags: none
Calls: OPEN