## Graphics Adapter Device Driver Reference

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### RMWx Commands

RMWx (Read/Modify/Write) commands are available in byte format (indexed or nonindexed) and in word format (nonindexed). A nonindexed port RMWx can be used for ports that have different read and write access I/O addresses. The syntax is as follows:

    RMWBI( indexport, dataport, index, andmask, ormask );
    RMWB( bytereadport, bytewriteport, andmask, ormask );
    RMWW( wordreadport, wordwriteport, andmask, ormask );

    <indexport>  ::= <pio variable>  |  <constant>
    <dataport>  ::= <pio variable>  |  <constant>
    <bytereadport>  ::= <pio variable>  |  <constant>
    <bytewriteport>  ::= <pio variable>  |  <constant>
    <wordreadport>  ::= <pio variable>  |  <constant>
    <wordwriteport>  ::= <pio variable>  |  <constant>
    <index>  ::= <constant>
    <andmask>  ::= <constant>
    <ormask>  ::= <constant>

For example:

    rmww(0x4ae8, 0x4ae8, 0x01, 0x00);