description of port mapping used by z80-mon for IN and OUT
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
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.
The instruction OUT (n),A
may select a certain bank, defined in the file
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
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.
z80-mon(1), z80-banks(5), z80-keyboard(5), z80-memory(5)