Editing SmartBox OS (section)

== Modules ==

The module is located at &8000 in memory, and should be a EPROM placed
in the second ROM socket in the controller (ie. the top RAM socket). This
module is primary designed to turn the Controller into a dedicated task,
making it perform some function from switch on. It could also be used to
add more permant JobCalls to the Controller, in the process taking up much
less RAM), but because of there being only one Module present this feature
is limited, and is much more suited to a collection of the user's own
personal routines.

For the OS to recognise a module as being in place the text "Module" is
looked for, the layout of a module should be like this (starting at
&8000):

{|class="wikitable"
!Offset!!Value!!Comment
|-
|0||"Module"||The OS checks for this string
|-
|6||0||End of check string
|-
|7||Language entry||Address of 'Language' entry
|-
|9||Service entry||Address of 'Service' entry
|-
|11||"<Module Title>"||Module title
|-
| ||0||End of Module title
|-
| ||"<Module part>"||Part Module Title
|-
| ||0||End of Part Module Title
|-
| ||"x.xx"||Part version number
|-
| ||&FF||End of parts list
|}

The language entry is a 2 byte value holding the address of the language
entry routine, this is called on reset, if the BCD is set correctly. A
value of less than &8000 means there is no valid language entry and any
language calls are ignored. If a RTS is made the OS carries on as it would
have if there wasn't a language call.

The service entry is a 2 byte value holding the address of the service
entry routine, this is called at various appropriate moments with service
numbers in A. A list of current calls is thus:

* 0	- Not used
* 1	- Unknown Job Code
* 2	- Centisecond call
* 3	- irq2 (unknown IRQ)
* 4	- internal_vec call (exit with A=0 to claim)
* 254	- RESET
* 255	- BRK

On exit all registers and flags should be preserved. For call 1 the
unknown job value is held in the Y register, the environment is held in the
X register, on exit, X should contain the flag, as A does from the exit of
unknownjob_vec. For the rest of calls, X and Y are undefined.

For both Service and Language entry points, a value of 0 means "there is
no valid routine" and the module isn't called for that type of entry.