Commodore 1581 - Chapter 7: Internal Disk Commands; 1581 Memory Map

CHAPTER 7
INTERNAL DISK COMMANDS
Expert programmers can give commands that directly alter the
workings of the 1581, much as skilled programmers can alter the
workings of BASIC inside the computer with Peeks, Pokes and Sys
calls. It is also possible to write machine language programs that load
and run entirely within the 1581, either by writing them into disk
memory from the computer, or by loading them directly from diskette
into the desired disk memory buffer. This is similar to loading and
running machine language programs in your computer.
As when learning to use Peek, Poke and Sys in your computer,
extreme caution is advised in using the commands in this chapter.
They are essentially machine language commands, and lack all of
BASIC'S safeguards. If anything goes wrong, you may have to turn the
disk drive off and on again (after removing the diskette) to regain
control. Do not practice these commands on any important diskette.
Rather, make a spare copy and work with that. Knowing how to
program a 6502 in machine language will help greatly, and you will
also need a good memory map of the 1581. A brief 1581 map appears
below.
Location
1581 MEMORY MAP
Purpose
0000-OOFF
0100-01FF
0200-02FF
0300-09FF
0A00-0AFF
0B00-0BFF
0C00-1FFF
4000-5FFF
6000-7FFF
8000-FEFF
FFOO-FFFF
Zero page work area, job queue, variables
Stack, variables, vectors
Command buffer, tables, variables
Data buffers (0-6)
BAM for tracks 0-39
BAM for tracks 40-79
Track cache buffer
8520A CIA
WD177XFDC
32K byte ROM, DOS and controller routines
Jump table, vectors
81