Commodore 1541-II - Memory Read

Other Resources:
More detailed information about Commodore disk drives can be found in these
books:
Inside Commodore DOS, by Immers & Neufeld (Datamost, cl984)
The Anatomy of the 1541 Disk Drive, by Englisch & Szczepanowski
(Abacus, cl984)
Programming the PET/CBM, by West (Level Limited, cl982)
The PET Personal Computer Guide, by Osborne & Strasmas
(Osborne/McGraw-Hill, c 1982)
MEMORY-READ
The disk contains 16K of ROM (Read-Only Memory), as well as 2K of RAM (Read-
Write Memory). You can get direct access to any location within these, or to the buffers
that the DOS has set up in RAM, 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, MR is correct, but MEMORY-READ is not a permitted alternate
wording.
FORMAT FOR THE MEMORY-READ COMMAND:
PRINT#15,t4M-R"CHR$(<address)CJ4R$(>address)CHR$(# of bytes)
where "<address" is the low order pari, and ">address" is the high order part of the
address in disk memory to be read. If the optional t4# of bytes" is specified, it selects
'how many memory locations will be read in, from 1-255. Otherwise, 1 character will be
read. If desired, a colon (:) may follow M-R inside the quotation marks.
ALTERNATE FORMAT:
PRINT#15,t4M-R:"CHR$(<address)CHR$(>address)CHR$(# of bytes)
The next byte read using the Get# statement through channel #15 (the error
channel), will be from that address in the disk controller's memory, and successive bytes
will be from successive memory locations.
Any Input# from the error channel will give peculiar results when you're using this
command. This can be cleared up by sending any other command to the disk, except
another memory command.
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