CustomVDU was written when I eventually got tired of seeing 14 mode-modules being loaded at boot, not being able to center them by software, and making myself a second VIDC clock. That's why it provides (almost) complete control over the VIDC. Giving absolute freedom to control a rather versatile chip like this one unfortunately makes it almost impossible to restrict the possibilities to the useful ones. Therefore, it's very easy to obtain a lot of useless results, and you're advised to read the last section of this text (Hints) if you don't know video signals or the VIDC too well.
CustomVDU consists of an application and a module. To avoid confusion, I'll violate my own rules and call the application '!CustomVDU' in this text.
First time installation of CustomVDU
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When !CustomVDU starts, it will scan all modules for modes, so if you want to collect all your mode-modules in CustomVDU, make sure to load them beforehand.
Run !CustomVDU. This will load the CustomVDU module and start the application. You may see a brief hourglass, depending on the speed of your machine :-)
Click on the icon, and the main window will open.
The 'Modes' Window
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Initially the module will be empty, containing no mode-definitions.
In the main window, the white modes are undefined, the grey/blue ones are defined, and the darkgrey/green ones are both defined and will be included in the module you're making.
You've probably got several mode-modules already, and if you want to include them, do the following:
Run all of them.
Start !CustomVDU, or if it's already running, select 'Update info' from the main menu.
Make sure that the info in 'Info' corresponds to your system. (see below)
Click on all the modes you want to include, so they're green.
Select 'Make module=>Normal', and a save box will appear.
OK or Return will save the module in your System:Modules directory, otherwise drag the icon somewhere else.
Now you can forget about all the mode-modules and simply load CustomVDU at boot.
Please note: The TV offset should be configured to 0. If you're using it, you can generate equivalent offsets with !CustomVDU.
Note1: If any of the modules were supposed to turn on an enhancer, you must tell CustomVDU to do likewise by editing the appropriate mode and selecting the proper vidc frequency (see below).
Note2: If you're booting a module to control the enhancer already, this will have to be killed. ('There Can Be Only One!')
The 'Modes' menu.
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The module will contain some information about your system, so you should ensure that this is correct by bringing up the menu, and looking under 'Info'.
Enter the monitor name. Leave the protection level 'On' at 2 µs for the moment. If you haven't got a video-enhancer, deselect the 'Present' button and ignore the rest.
If you've got one, select the 'Present' button, and enter the frequency in MHz. Also, select the way to control the enhancer:
AUX1, High=On : Turned on by writing 1 to the AUX1 bit.
AUX1, High=Off: Turned off by writing 1 to the AUX1 bit.
AUX2, High=On : Turned on by writing 1 to the AUX2 bit.
AUX2, High=Off: Turned off by writing 1 to the AUX2 bit.
A500, High=xxx: Turned on and off by Risc-Os, 'High' state doesn't matter.
This is the choice for A540/A5000 owners.
If there's some of this info you do not know, contact the person who fitted the enhancer. If you're a A5000 owner who doesn't know your enhancer's frequency, it's 36 MHz.
'Update info' will scan through the modes, reading info about them, just as it is done when the program is started. You should use it to update the 'Modes' window when a mode-defining module is started or killed.
'Make module' is used to generate a CustomVDU module from the current settings. Three entries are provided, each making a different kind of module.
'Normal': This is the ordinary module, containing all the green/grey
modes and a few commands (see below).
'Just modes': This is the same as above, but the commands (except
*CustomOn/Off) are not included.
'Mode xxx': This module will only provide the chosen mode, and no
commands. It is not available if you've pressed Menu over an
undefined mode.
If you press menu over a defined mode, the 'Mode xxx' submenu can be
reached. Firstly 'Info':
It's a rather large window containing (almost) all information about the selected mode. Nothing can be edited here, but the window looks similar to the editable one, so it may be a good idea first to look at the info about some well-known modes before attempting to edit or make one yourself.
The info is not self-explanatory unless you know about video signals, but I'll make a complete explanation in this file, later.
The 'Clone' submenu obviously makes a copy of the selected mode.
'Default' is only available for modes 0-21 & 23-28 and will simply reset the mode to the default design.
'Easy setup' was meant to become a quick way of setting up a mode, but I haven't implemented that yet.
Editing a mode
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Clicking Adjust on a mode will open the edit-window. This window contains all information about the mode, and may look a bit confusing at first. You'll get used to it when you learn where the relevant info is. I'll take it from the top.
The 'Mode xxx' is the mode number and cannot be changed.
The 'Enhancer' can be either on, off or not present, and depends on the pixel rate, so it can't be changed directly.
The Pixel rate is the pixel rate i.e. the number of pixels per second. The possible pixel rates are calculated when you enter the enhancer frequency in the 'System Info' box. You can change it by clicking on it.
(Changing the values is generally done by clicking on them. Select increases and Adjust decreases, unless it would become illegal and/or damage your monitor, in which case it will stay where it is.)
The middle part of the window is the physical info which is sent to the VIDC.
The right part are the logical values, which Risc-Os knows about.
In most cases these parts will reflect similar values, but it's sometimes useful for them to differ (e.g. double-pixel modes, character enlargement/ reduction etc.) Because of this, the 'transferring arrow' button is very important and often used. It will read the physical values, assume a lot of things, and generate some logical ones. Because of the assumptions, it might not be what you wanted, but usually it will.
To the left is the actual VIDC register values. Most of these corresponds to one or more of the values above and both will change when you alter one. Use of these obviously requires knowledge about the VIDC, I can't give you that now, but here's a list of the abbreviations:
HCR: Horizontal Cycle Reg.
HSWR: Horizontal Sync Width Reg.
HBSR: Horizontal Border Start Reg.
HDSR: Horizontal Display Start Reg.
HDER: Horizontal Display End Reg.
HBER: Horizontal Border End Reg.
HIR: Horizontal Interlace Reg.
VCR: Vertical Cycle Reg.
VSWR: Vertical Sync Width Reg.
VBSR: Vertical Border Start Reg.
VDSR: Vertical Display Start Reg.
VDER: Vertical Display End Reg.
VBER: Vertical Border End Reg.
DMA: DMA request delay
Bpp: Bits per pixel
Rate: Clock division selection
The 4 arrows on the mini-iconbar moves the display.
the rest of the arrows moves the corresponding border edge.
The 'Store' button will store the current values and you must remember to click here at least when you're finished, if you want to keep your edited mode.
The 'Undo' button is not a proper undo, it just recalls the last values stored. I.e. only press Store, when you've got some reasonable values.
The 'Instant effect' button requires a certain amount of knowlegde about what you're doing, if you don't want to end up with an even worse result. When this option is active, the display will change instantly when you alter a value. You'll get a totally garbled display if you alter anything important like the number of colours, but this feature is marvelous when it comes to centering the display etc. So use it with care. If you should end up with nothing usable on the screen, Escape will act like Undo, i.e. reset to the last values Stored. So press 'Store' when you've got a readable display only.
Note1: The instant effect uses a temporary mode (127), so don't change mode by any other means while it's active.
Note2: The width and height buttons resize the display symmetrically around the center with a step of 4 and 2 pixels. The vidc can do one half of this, and to get those values, alter the vidc registers yourself (HDSR,HDER,VDSR,VDER, see above). When the border would have gone beneath the display or on top of the syncs, the value won't change. This can be annoying if the display isn't centered yet, so if it happens, use the vidc-registers again.
A few Hints...
The monitor-protection is only relevant for some multisync monitors. I've got a Philips CM8873, and it simply won't die. Most multisyncs should be able to cope with Hsync widths of 2 µs and above, so this is the default value. If you've got a normal monitor, a vga monitor or the CM8873 you can simply turn it off, otherwise the 'trial and scream' method is not exactly good, but the only one, as the critical values are almost never documented.
Some astoundingly ugly displays can be generated from eg. mode 9 by setting 'Xcoords/pixel' and 'Ycoords/pixel' to 1. Might even be useful for some.
When you're editing a mode, the following method is almost fool-proof
(it's how I do it :-)
1. Click 'Store'.
2. Repeat this:
3. Adjust one or two parametres.
4. Click 'Get from physical'
5. Click 'Instant effect' on.
6. Observe the incredible useless display.
7. Click 'Instant effect' off.
8. Click 'Store' if the display was readable.
9. Until you're satisfied.
If your otherwise perfect mode appears shifted one or more 'chars' to the left, try adjusting the DMA delay.
If you want to use the desktop in a mode, ensure that the number of x- pixels is a multiple of 8. If the CLI or other VDU4 activity is going to work, the y-resolution must also be a multiple of 8.
This is PD, spread at will. I've got the copyright of the application and the modules generated though you're free to include the single-mode modules in a product of your own.
Please report any problems or comments through FidoNet to Thomas Olsson
(2:234/101.1).
All this software is provided "as is"; Thomas Olsson makes no warranty, express or implied, of the merchantability of this software or its fitness for any particular purpose. In no circumstances shall Thomas Olsson be liable for any damage, loss of profits, or any indirect or consequential loss arising out of the use of this software or inability to use this software, even if Thomas Olsson has been advised of the possibility of such loss.
The main program is written in Basic and is rather big, about 73K. In order to reduce dload time, disk space, load time, program memory, variable space and execution time, it's crunched. However, if you want to look at the program, perhaps for reasons of customising it even further, the source will be available from me, and probably soon from your nearest BBS too. I can't spread the cruncher as it's copyrighted, so if you've made major improvements to the program, please return it to me, and I'll release a new crunched version.
The technical info about the application which is not given above is too extensive to be included here, but the source is fairly readable (I think :-), nice long variables and routine-names (again an advantage in crunching) so if you usually feel good about reading other peoples programs, you'll have a fair chance here.
The module can do a few other things as well as providing your favourite modes. Commands and swi's follows; for further details you can find the module-source in the application sourcecode.
*WimpMode <mode> will set the wimpmode to <mode> by issuing the
SWI "Wimp_SetMode" with R0=<mode>
There seem to exist a convention regarding that whoever
is controlling the enhancer, has the responsibility to
provide a 'WimpMode' command, so here it is.
*SampleRate <period> will program the sound system sample period to the
value given. If the enhancer is on, however, the value
actually given to SWI "Sound_Configure" will have been
multiplied by a factor in order to minimise the pitch
difference.
*CustomOff will remove all mode-grabbing activity etc. It's almost
the same as killing the module, but you've still got
the WimpMode command, and you can always use:
*CustomOn which will wake the module up, and start controlling
the vdu again.
Software interrupts.
SWI base is &C1500, which is chosen at random among the user-swi's.
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SWI &C1500, "CV_WannaAlter"
On entry: R0 = Mode
On exit: R0 = -1 or 0 (Yes or No)
R1 corrupted
R3 = Pointer to VIDC list if Yes
R4 = Pointer to ModeVars if Yes
R5 = Enhancer status if Yes, otherwise corrupted
This SWI is used to ask CustomVDU whether it is planning to modify the
mode given on entry by any means. If it is, the parametres which will be
given to the OS at the modechange service call are returned, along with
the on/off flag for the enhancer (0=Off).
If CustomVDU has been disabled using *CustomOff, this SWI will always
return 'No' in R0.
Note: The enhancer flag has nothing to do with the actual value stored in
LatchB; the polarity and position of this bit is constant, and set at
assembly time from the 'Info' window.
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SWI &C1501, "CV_TestMode"
On entry: R0 = Mode to react upon (or -1 to disable testmode)
R1 = Pointer to VIDC list to use
R2 = Pointer to ModeVar list to use
R3 = Enhancer status to use
On exit: All registers preserved
This SWI is used to (temporarily) set up a mode, usually for test
purposes. It is used by !CustomVDU when 'Instant effect' has been
activated, but can also be used by other programs as an easy way of
setting up a non-standard mode. The mode number can be anything from 0 to
127, or -1 to stop grabbing the mode.
The lists pointed to by R1 and R2 and the flag in R3 is copied into
CustomVDU's workspace, and thus need not to be preserved until the
modechange occurs.
No checks are made on the values in the lists, so you must be careful.
A useful way of doing this is by issuing "CV_WannaAlter" first to get a
proper list, and then modifying the appropriate values only.
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SWI &C1502, "CV_Enhancer"
On entry: R0 = Status (-1=On, 0=Off)
On exit: All registers preserved
This SWI will 'manually' turn the enhancer on or off.
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SWI &C1503, "CV_SysInfo"
On entry: R0-R5 = Whatever values you want thrown away
On exit: R0 = Pointer to 0-terminated monitor name
R1 = Protection level in µs
R2 = Enhancer presence (-1 or 0)
R3 = Enhancer frequency in MHz, fixed point before bit 16
R4 = LatchB mask
R5 = Bit polarity for turning the enchancer on
This SWI returns some info about the system for which the module was
generated. It is exactly the same as given in the 'Info' window before
assembly. The number in R3 is fixed point, so if the frequency for example
is 33.5 MHz, R3 would become 33.5*&10000 or &00218000.
The enhancer mask is 0 in all bits except the one that controls the
enhancer. However, the mask can be all zeros (meaning A5000 style), and
the enhancer is then controlled by Risc-OS.
The enhancer bit polarity is a sign (-1 or 0), if it's -1, the enhancer is
turned on by writing a 1 in the appropriate bit in LatchB.
