Chapter 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.
1581 ÄJEMOKY MAP
Location
Propose
0000-00FF 0100-0 IFF 0200-02FF 0300-09FF 0A00-0AFF 0B00-0BFF 0C00-1FFF 4000-5FFF 6000-7FFF 8000-FEFF FF00-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
WD177X FDC
32K byte ROM, DOS and controller routines Jump table, vectors_
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