The information in this appendix provides a useful reference to the memory locations of the Atari computer series. While most documented locations have stayed backwardly compatible, some have changed in meaning. Software programmers directly accessing these locations should carefully consider the possibility that a location may move or not even exist in a newer version of the OS. For this reason many OS functions exist to manipulate system variables, vectors, interrupts, and devices. These should always be used, if possible, as an alternative to directly accessing hardware registers, vectors, interrupts, and variables.
In addition to those considerations mentioned above, directly accessing hardware registers can cause damage to hardware if not done correctly. In particular, improper use of the Falcon030 video registers could damage an attached monitor. Likewise, use of the floppy and hard drive registers can cause data loss and drive damage. For these reasons, it is strongly recommended that you avoid using hardware registers when possible, and when otherwise unavoidable, they should be used with extreme care.
For each Atari computer that a specific hardware location is valid for, the appropriate box will be shaded. Following is a key to several abbreviations and concepts used in this guide:
|
| Occupies one byte (8 bits). |
|---|---|
|
| Occupies one WORD (16 bits). |
|
| Occupies one longword (32 bits). |
|
| Occupies the odd WORD of a LONG. |
|
| Occupies the even WORD of a LONG. |
|
| Occupies the odd BYTE of a WORD. |
|
| Occupies the even BYTE of the WORD. |
|
| Location is Read-Only Memory |
|
| Location is Read-Write Memory |
|
| Location is hardware-mapped |
|
| Location addresses VME address space |
|
| Not applicable |
|
| Read-only location |
|
| Write-only location |
|
| Read-write location |
|
| Reserved |
|
| Either not assigned or undocumented (hardware developers should always consult Atari before mapping a third-party device to a hardware location). |