Can somebody please test the following code fragment on real hardware and report back the result?
Code:
lda #0
sta $22
lda #1
sta $122
ldx #$F0
lda $32,X
Does A contain 0 or 1?
Both
6502 Assembly Language Programming by Lance Leventhal and
Programming the 6502 by Rodney Zaks are silent about whether the effective address wraps to stay within the zero page.
On page 102 of
Programming the 65816 https://web.archive.org/web/20221112231 ... manual.pdfQuote:
On the 6502 and 65C02, and in they<sic> 6502 emulation modes of the two sixteen-bit processors, indexing past the end of the direct page wraps to the beginning of the direct page, as Fragment 7.9 shows. The index and the direct page array base are added, but only the low eight bits of the sum specify the direct page offset of the effective address. So in Fragment 7.9, while the base of $32 plus the index of $F0 equals $122, only the $22 is kept, and the accumulator is loaded from dp:$22.
Fragment 7.9 is
Code:
A2F0 LDX #$F0 set up an index of $F0
B532 LDA $32,X load accumulator from dp:$22
Does the Dormann test suite test for things like this?
Thanks in advance.
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