Xycom XVME-678 Manual page 101

XVME-678/688 Manual
July 1994
To maintain numeric consistency, the bytes of a 16-bit or 32-bit quantity must be swapped in software
prior to transferring them to the VMEbus, or afterward if the data has been read from the VMEbus. The
following code example illustrates this necessity:
value equ
CONREG 1
mov
12345678h
equ 30h
aX,OEOOOh
mov eS,ax
in al,CONREG_1
and al,9Fh
or al,40h
out CONREG_1,al
mov
xchg
ror
xchg
mov
eax,value
ah,al
eax,16
ah,al'
es:[O],eax
;Point to Real Mode Window
; Select VMEbus Standard address space
;Read value into register
;Swap low-order bytes
;Swap the words
;Swap high-order bytes (EAX=78563412h)
;32-bit transfer to VMEbus
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