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Libraries:
expansion.library
AddBootNode
AddConfigDev
AddDosNode
AllocConfigDev
AllocExpansionMem
ConfigBoard
FindConfigDev
FreeConfigDev
FreeExpansionMem
GetCurrentBinding
MakeDosNode
ObtainConfigBinding
ReadExpansionByte
ReadExpansionRom
ReleaseConfigBinding
RemConfigDev
SetCurrentBinding
WriteExpansionByte
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Docs » Autodocs » expansion.library » WriteExpansionByte
WriteExpansionByte - write a byte nybble by nybble.
WriteExpansionByte( board, offset, byte )
A0 D0 D1
(Not typically called by user code)
WriteExpansionByte writes a byte to a new-style expansion
board. These boards have their writeable data organized
as a series of nybbles in memory. This routine writes
two nybbles in a very careful manner to work with all
types of new expansion boards.
To make certain types of board less expensive, an expansion
board's write registers may be organized as either a
byte-wide or nybble-wide register. If it is nybble-wide
then it must latch the less significant nybble until the
more significant nybble is written. This allows the
following algorithm to work with either type of board:
write the low order nybble to bits D15-D12 of
byte (offset*4)+2
write the entire byte to bits D15-D8 of
byte (offset*4)
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.
board - a pointer to the base of a new style expansion board.
offset - a logical offset from the configdev base
byte - the byte of data to be written to the expansion board.
EXAMPLES
WriteExpansionByte( cd->BoardAddr, ECOFFSET( ec_Shutup ), 0 );
WriteExpansionByte( cd->BoardAddr, ECOFFSET( ec_Interrupt ), 1 );
ReadExpansionByte(), ReadExpansionRom()
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