QI am confused about the service routines and data areas passed in the _ADBOp call.
What does it all mean?
A That 's a good question. The ADBOp call looks like this:
FUNCTION ADBOp (data:Ptr; compRout:ProcPtr; buffer:Ptr;
commandNum:INTEGER) : oserr;
data is a pointer to the "optional data area." This area is provided for the use of the
service routine (if needed).
compRout is a pointer to the completion or service routine to be called when the
_ADBOp command has been completed. It has the same meaning as the service routine
passed to the _SetADBInfo call.
buffer is a pointer to a Pascal string, which may contain 0 to 8 bytes of information.
These are the 2 to 8 bytes that a particular register of an ADB device is capable of
sending and receiving.
commandNum is an integer that describes the command to be sent over the bus.
There is some confusion over the way the completion routines are called from _ADBOp.
You can call these routines in one of three ways, depending on what you want to do:If
you do not wish to have a completion routine called, as in a Listen command, pass a NIL
pointer to _ADBOp.
If you wish to call the routine already in use by the system for that address (as
installed by _SetADBInfo), call _GetADBInfo before calling _ADBOp, and pass the
routine pointer returned by _GetADBInfo to _ADBOp.
If you wish to provide your own completion routine and data area for the _ADBOp call,
simply pass your own pointers to the _ADBOp call.
Remember, there should rarely be a reason to call _ADBOp. Most cases are handled by
the system's polling and service request mechanism. In the cases where you must call
_ADBOp, don't do it in a polling fashion, but as a mechanism for telling the device
something (for example, telling the device to change modes or, in the case of the
extended keyboard, to turn an LED on or off).
QThe AppleTalk spec claims a data rate of 230.4 kbaud, which should require a
3.6864 MHz input to the SCC, but RTxCB on the Macintosh carries a 3.672 MHz clock.
How does the AppleTalk driver reconcile this discrepancy and what frequency should I
use?
A The SCC contains a phase-locked loop that can lock on and synchronize with
AppleTalk transmissions whose clock rates are not exactly to specifications, so
everything is fine as long as both ends of the communication are using approximately
the same clock frequency. If you are designing your own AppleTalk hardware from
scratch, it's easiest to use a 3.6864 MHz oscillator and a Z8530. This has been tested
and works just fine.
QWhen I fill in the fields of MPW's Name Binding Protocol (NBP) EntityName
structure, AppleTalk doesn't recognize the entity, even though I know it's out there.
What's going on?
A The real definition of EntityName is three PACKED strings of any length (32 is just
an example). No offsets for Asm are specified since each string address must be
calculated by adding the length byte to the last string ptr. In Pascal, string(32) will
be 34 bytes long (fields never start on an odd byte unless they are only 1 byte long).
So correct-looking interfaces for Pascal and C will be generated, but they won't be the
same, which is OK since they aren't used.
The point here is that you should never try to access the fields of the EntityName field
directly. The only reason the type is defined at all is so that you can allocate
EntityName variables that will hold the largest possible EntityName. To fill in an
EntityName record, you should call the NBPSetEntity routine.QHow do I determine
which language is in use on the system?
A Every language has a corresponding KCHR resource. Inside Macintosh, volume I,
page 499, lists the currently defined country codes, which are the resource IDs of the
KCHR resources.
To find out which KCHR is in use, call the Script Manager function GetScript with the
verb smScriptKeys. This call returns the ID of the KCHR resource in use (not the ID of
the KEYC resource, as stated in Inside Macintosh, volume V, page 312).
Here's a bit of C code that determines which KCHR is being used:
#include <script.h> ... kchrID = GetScript(smRoman, smScriptKeys);
kchrID will be 1 when booted in French, 2 when booted in British English, and so on.
QWhen I use DeleteRevision to remove old revisions from my Projector database, the
actual size of the ProjectorDB file doesn't decrease much. How can I make the file
smaller?
A Projector does not currently compact files. What it does is mark the areas of the
database that are now free and put them into a free page list. This effectively puts holes
into your database, holes that are subsequently filled up when you add more revisions.
Your database will get smaller only if the free pages are at the end of the file; then
Projector will shrink the file. However, there is very little you can do about
controlling this situation. If you absolutely must have a smaller database, then all you
can do is check everything out, orphan the files, and create a new database. The
disadvantage of this method is that you lose all your revisions and revision comments.
The Projector team is aware of the need to compact the database. The team is currently
studying the feasibility of adding such a function.
QHow does MultiFinder decide the starting order when you set multiple applications to
start up under MultiFinder with Set Startup? Is there any way to control the order?
A Here's the lowdown on MultiFinder application startup procedures.
From the Finder, launch, in order, application A, application B, and then application C.
Switch to the Finder, choose Set Startup, and select Open Applications and DAs. The
launch order is now application C, then application B, then application A. Regardless of
the type of view from the Finder, the startup order is from top to bottom,
respectively.
If you'rereally interested, the Finder Startup file in the System Folder contains the
applications and files to be launched and the order in which they should be launched.
This file contains a 'fndr' ID = 0 resource that stores the applications and their
pathnames. The applications are launched in the order in which they are listed. You can
use ResEdit to view the resource and see the filenames, the VRefNums, and the volume
names of the startup applications. You can also tell the number of startup applications
by the number at the beginning of the resource (that is, 0000 0001 means one item).
Remember, however, that this informmation is valid only for pre-System 7.0
MultiFinder environments.