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)