Commodore Amiga A500 Technical Reference Manual page 72

SYSTEM/LIBRARIES/
EXPANSION/
READEXPANSIONBYTE
BUGS
NAME
ReadExpansionByte read a byte nybble by nybble.
SYNOPSIS
byte = ReadExpansionByte( board, offset )
DO AO DO
FUNCTION
ReadExpansionByte reads a byte from a new-style expansion board.
These boards have their readable data organized as a series of
nybbles in memory. This routine reads two nybbles and returns the
byte value.
In general, this routine will only be called by ReadExpansionRom.
The offset is a byte offset into a ExpansionRom structure. The
actual memory address read will be four times larger. The macros
EROFFSET and ECOFFSET are provided to help get these offsets
from C.
INPUTS
board —a pointer to the base of a new style expansion board, offset
— a logical offset from the board base
RESULTS
byte — a byte of data from the expansion board, or ■ 1 if there was
an error reading from the board.
EXAMPLES
byte = ReadExpansionByte( cd->BoardAddr. EROFFSET( er_Type ) )
: ints = ReadExpansionByte(cd->BoardAddr, ECOFFSET
(ec_Interrupt));
EXCEPTIONS
SEE ALSO
WriteExpansionByte. ReadExpansionRom
BUGS
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