DragonFly On-Line Manual Pages

Z80-PORTS(5)                     Port mapping                     Z80-PORTS(5)

NAME
       description of port mapping used by z80-mon for IN and OUT

DESCRIPTION
       Because the IN and OUT instructions communicate with the outside their
       effect is environment/OS dependend.  Port access can be either directly
       clock synchron or asynchron and buffered.  In the later case all
       effected ports by the IN and OUT instructions are realized as a binary
       file named .Z80_ports buffering the data.  Then this file must be read-
       and writable and should contain 256 bytes.  In the case, that only
       directly synchron port access by other hardware components is wanted,
       this file .Z80_ports should not exist, or must be at least nonreadable
       to not interfere with the system bus.

       The user has the option to reserve some ports for bank switching.

bank switching
       The instruction OUT (n),A may select a certain bank, defined in the
       file banks.  The value of A selects the position the bank is mapped on.
       Some banks ignore the value A, and are always mapped onto a predefined
       position.

Two special ports for character input and output
       are connected to stdin and stdout. Typically these are the ports 0 and
       1 in UNIX. Appropriate hardware is already attached to enable
       nonblocking keyboard reading (be aware that this might interfere which
       z80-mon) and output on a one line display inside z80-mon user
       interface.

SEE ALSO
       z80-mon(1), z80-banks(5), z80-keyboard(5), z80-memory(5)

Z80-PORTS Version 2.3             08 Jun 2005                     Z80-PORTS(5)