Commodore 1581 - Memory-Read Command

NOTE
The 1581, as well as other Commodore peripherals, is
designed to support interfacing via software command
structures. The software commands provided in the 1581
allow for a smooth and controllable interface between the
peripheral and CPU. Although Commodore has provided
the mechanism enabling users to load and execute their
own machine language programs within the 1581 system,
please keep in mind that Commodore reserves the right to
change ROM, RAM, I/O and hardware structure at any time.
Consequently, if the defined software interface is bypassed,
future compatibility of the user's machine language soft
ware within the 1581 may be in question. The 1581 was not
designed primarily as a user programmable device, but
Commodore recognizes that certain operations (such as
copy protection) cannot be easily achieved without this
ability.
If you find it necessary to use machine language within
the 1581, use the jump table listed in this chapter and
Chapter 10. That will lessen the possibility of incompatibil
ity if a future version of the 1581 changes internally. Also, let
the controller work for you on the physical level by request
ing its help via the JOB QUEUE. That too will greatly in
crease the likelihood of future compatibility.
MEMORY-READ
The 6502 has an address space from $0000 — $FFFF. You can get
direct access to any location within this by using memory commands.
MEMORY-READ allows you to select which byte or bytes to read from
disk memory into the computer. The MEMORY-READ command is the
equivalent of the BASIC Peek() function, but reads the disk's memory
instead of the computer's memory.
-NOTE
Unlike other disk commands, those in this chapter
cannot be spelled out in full. Thus, M-R is correct, but
MEMORY-READ is not a permitted alternate wording.
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