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Diffstat (limited to 'test/getramsize.s')
| -rw-r--r-- | test/getramsize.s | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/test/getramsize.s b/test/getramsize.s new file mode 100644 index 0000000..cd2c69b --- /dev/null +++ b/test/getramsize.s @@ -0,0 +1,45 @@ +; Find the end of RAM, and get the size of the RAM. +; Written by mr b0nk 500 <b0nk@b0nk.xyz>. + +RAMSTART = $20000 +MAGIC = $AA + +.org 0 +; End of RAM. +ptr1: + .res 8 + +.org $8000 +reset: + cps ; Boilerplate reset code. + ldx.w #$FFFF ; + txs ; + and #0 ; Reset A. + tax ; +start: + lda.d #RAMSTART ; Set the starting point of getramsize to the start of our RAM. + jsr getramsize ; Get the size of the RAM. + bra start ; + + +getramsize: + sta.q ptr1 ; Set the end of RAM pointer to the argument. + and #0 ; Reset A. + tab ; Reset B. + lda #MAGIC ; Set A to a magic number. +@loop: + sta (ptr1) ; Write the magic number to the current end of RAM. + cmp (ptr1) ; Is the value in RAM, the same as the magic number we wrote? + bne @end ; No, so we're done. + inc.q ptr1 ; Yes, so increment the end of RAM pointer. + inb ; Increment the byte count. + bra @loop ; Keep looping. +@end: + inc $0110 ; + rts ; End of getramsize. + +.org $FFC0 +.qword reset + +a +d |