Service manual

Chapter 4 E01 Circuit description
FileStore Service Manual 22
Higher values in this page will access the same registers as above if taken modulo &40.
Values in square brackets above are also alternate addresses for the various registers. Note
that addresses are subject to change, and this should be borne in mind when designing
software to address these registers.
4.13.4 Machine Operating System function calls
The file server MOS provides a subset of the BBC MOS interface. It is not necessarily the
case that any test programs running in place of the file server will be able to obtain all the
desired support from the MOS. Such test programs should however be written with an
awareness of the MOS in mind. In particular, it is recommended that the contents of the
hardware registers and interrupt vectors are saved and restored over the execution of a test
program, and the stack pointer restored to its value on entry.
The file server MOS provides the following functions, at the standard addresses:
OSASCI, OSNEWI, OSWRCH
These have the same specification as for the BBC MOS, except that the character in A is
always inserted into the printer output buffer, not the current output stream buffer. If the
buffer is full, these routines wait until there is room to store the character.