The BBC and Master Computer Public Domain Library
Copy FWB to FWA
Submitted by Steve Fewell
Routine: acopyb
Name: Copy FWB to FWA
Starting Address: &8349
Entry criteria: None
Exit: Copies the value of the FWB to the FWA.
Description:
Sets every byte of the FWA to a copy to the corresponding FWB byte as follows:
Byte Description |
FWB |
FWA |
| Sign | &3B ---> | &2E |
| Overflow | 00 ---> | &2F |
| Exponent | &3C ---> | &30 |
| Mantissa 1 | &3D ---> | &31 |
| Mantissa 2 | &3E ---> | &32 |
| Mantissa 3 | &3F ---> | &33 |
| Mantissa 4 | &40 ---> | &34 |
| Mantissa 5 / Rounding | &41 ---> | &35 |
The FWA now holds the same value as the FWB.
Disassembly for the Copy FWB to FWA routine
| 8349 | ; | 165 059 | A5 3B | LDA &3B |
| 834B | . | 133 046 | 85 2E | STA &2E |
| 834D | d/ | 100 047 | 64 2F | STZ &2F |
| 834F | < | 165 060 | A5 3C | LDA &3C |
| 8351 | 0 | 133 048 | 85 30 | STA &30 |
| 8353 | = | 165 061 | A5 3D | LDA &3D |
| 8355 | 1 | 133 049 | 85 31 | STA &31 |
| 8357 | > | 165 062 | A5 3E | LDA &3E |
| 8359 | 2 | 133 050 | 85 32 | STA &32 |
| 835B | ? | 165 063 | A5 3F | LDA &3F |
| 835D | 3 | 133 051 | 85 33 | STA &33 |
| 835F | @ | 165 064 | A5 40 | LDA &40 |
| 8361 | 4 | 133 052 | 85 34 | STA &34 |
| 8363 | A | 165 065 | A5 41 | LDA &41 |
| 8365 | 5 | 133 053 | 85 35 | STA &35 |
| 8367 | ` | 096 | 60 | RTS |
