DEVNO - Hardware device number
Hardware device number used in Sintran III, used in the IOX(T) instruction to read/write registers on a controller/interface.
There are normally four registers assigned to each simple interface (a complex interface may have more registers assigned to it), but not all registers must necessarily be in use.
A device which is both input and output capable (like a terminal interface) will have eight registers, one set for the input part and one set for the output part.
This is the typical register usage:
When a direction of a data signal is specified in a table, the controller (or the host) is always to the left and the device in action to the right
(unless otherwise stated). F.ex the floppy disc drive signal INDEX is marked with ⇐ which means it is FROM drive TO the controller.