Timeline for How to transfer the address of a data block into zero page using the Merlin 8 assembler on my Apple //e?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 30, 2020 at 14:44 | comment | added | fadden |
"Truncating to fit available data size" is assembler-specific. The datasheet recommends, but does not define, assembler behavior. For example, in ca65, LDA #DATA / 256 will work, but LDA #DATA / 16 will not ("range error"). Merlin is aggressive when it comes to truncating expression results, more so than the other popular 65xx cross-assemblers.
|
|
| Mar 30, 2020 at 13:49 | comment | added | Chromatix | @fadden Additionally, as both the OP's example and the above table suggest, immediate operands are in fact truncated to fit the available data size, without generating an error. | |
| Mar 30, 2020 at 11:32 | comment | added | Chromatix | @fadden The question was in the context of the 6502 specifically. I referred to the '816 datasheet as it was the one place I knew I could find those "standard" modifiers documented. | |
| Mar 30, 2020 at 4:39 | comment | added | fadden |
Most assemblers (64tass, ACME, ca65) treat #< and #> as byte-selection operators. Merlin treats them as shift+mod operators. For 8-bit code the effect is the same, but it can surprise you with 16-bit code. Your DATA DIV 256 example might throw an error if you attempted that with a 24-bit constant for an 8-bit immediate instruction.
|
|
| Mar 30, 2020 at 2:18 | history | edited | Chromatix | CC BY-SA 4.0 |
added 123 characters in body
|
| Mar 30, 2020 at 2:10 | history | answered | Chromatix | CC BY-SA 4.0 |