83Plus:OS:RST Routines
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Revision as of 20:30, 2 June 2005 by 68.41.6.124 (Talk)
Introduction
The Z80 restart instruction, or RST, can be used instead of a B_CALL for some system entry points. The advantage is that using the RST instruction takes only one byte, instead of the three bytes required for a B_CALL, and is very quick when compared with the relatively large overhead inherent of a B_CALL.
RST Routines
All the RST routines work exactly the same as the corresponding B_CALLs:
| B_CALL | RST |
| FindSym | rFindSym |
| PushRealO1 | rPushRealO1 |
| Mov9ToOP1 | rMov9ToOP1 |
| FPAdd | rFPAdd |
Example
rst rFPAdd
Equates
rOP1ToOP2 EQU 08h rFindSym EQU 10h rPushRealO1 EQU 18h rMov9ToOP1 EQU 20h rFPAdd EQU 30h
Remarks
You cannot define your own RSTs; they are part of the operating system.
rst 00 is the OS reset rst 28h is BCALL rst 38h is the interrupt routine
