Search found 167 matches

by Sarah
Mon Oct 07, 2013 12:32 pm
Forum: Dragon General
Topic: copyrights on old ROMs ?
Replies: 4
Views: 529

Re: copyrights on old ROMs ?

I think the rumours 20 or so years ago were that the copyright passed to Prudential plc however I've no idea whether or not that holds any truth or what the current situation may be. It's difficult to imagine that anyone at Prudential plc would have the slightest idea about such an old low value ass...
by Sarah
Sun Oct 06, 2013 9:44 pm
Forum: Dragon General
Topic: Dragon emulator written in Python ???
Replies: 105
Views: 18775

Re: Dragon emulator written in Python ???

That's a little to hight for me, at the moment. e.g. what is "mapmode0" ? The map mode basically controls the configuration of RAM and ROM for a system using an MC6883 (SAM). You can read full details about how it decodes addresses in the data sheet: http://images.ihscontent.net/vipimages/VipMaster...
by Sarah
Sun Oct 06, 2013 5:04 pm
Forum: Uploads
Topic: Rebound from Your Computer magazine
Replies: 3
Views: 836

Re: Rebound from Your Computer magazine

I suppose "-(A1=31)" will evaluate to 1 when A1 reaches 31 and 0 otherwise.

So it makes the right-hand border draw at X=63 instead of X=62 and therefore outlines the screen edge a little more neatly with the published expression.
by Sarah
Sun Oct 06, 2013 2:49 pm
Forum: Dragon General
Topic: Dragon emulator written in Python ???
Replies: 105
Views: 18775

Re: Dragon emulator written in Python ???

This is what to do at reset:
  • Set mapmode0 and reinstate the mapmode0 ROM
  • Set DP to #0
  • Set the I and F flags in CC to mask interrupts
  • Load PC from $FFFE
That's all. You shouldn't need a value for S as code executing after reset cannot assume it to be set.
by Sarah
Sun Oct 06, 2013 3:43 am
Forum: Dragon General
Topic: Dragon emulator written in Python ???
Replies: 105
Views: 18775

Re: Dragon emulator written in Python ???

jedie wrote:So i set the initial stack pointer to $7E36, is that right?
Not really, no. The ROM loads S with a value after detecting how much RAM is installed.

It should wrap around between 0 and $FFFF just like other registers.
by Sarah
Sat Oct 05, 2013 2:53 am
Forum: Dragon General
Topic: Comparison of Dragon Assemblers?
Replies: 14
Views: 2077

Re: Comparison of Dragon Assemblers?

I always had the impression that the DREAM family was the most popular or best regarded assembler - not sure if any reviews or stats ever provided the basis for this belief. It was originally licensed by Dragon Data so probably inherited some status that way.
by Sarah
Wed Oct 02, 2013 6:48 pm
Forum: Hints and Tips
Topic: Howto try small machine code programs in BASIC ?
Replies: 53
Views: 6406

Re: Howto try small machine code programs in BASIC ?

If you're getting FULL when trying to start DREAM then you haven't allocated any/enough memory with CLEAR. The built-in editor is pretty easy to use IMO; certainly much easier than BASIC. There's not much more you need to know to get started and most of it is on page 27 of the manual. BREAK then A t...
by Sarah
Wed Oct 02, 2013 11:47 am
Forum: Hints and Tips
Topic: Howto try small machine code programs in BASIC ?
Replies: 53
Views: 6406

Re: Howto try small machine code programs in BASIC ?

Are you doing all your assembly by hand? You'd surely find it easier to use an assembler like DREAM. It's straightforward to launch (execute) the assembled program within DREAM too. If you have ALLDREAM then it comes with the DREAMBUG debugger built-in, which isn't especially easy to use but can be ...
by Sarah
Tue Oct 01, 2013 11:02 pm
Forum: Hints and Tips
Topic: Howto try small machine code programs in BASIC ?
Replies: 53
Views: 6406

Re: Howto try small machine code programs in BASIC ?

jedie wrote:But can i print the value (in this case $58 == 88) of accumulator A to screen?
Here are some options:
  • Use a debugger
  • Make a simple routine that outputs the hex value using two ascii characters
  • JSR 38266 outputs the decimal value of D register
by Sarah
Tue Oct 01, 2013 12:41 am
Forum: Hints and Tips
Topic: Howto try small machine code programs in BASIC ?
Replies: 53
Views: 6406

Re: Howto try small machine code programs in BASIC ?

I wouldn't really recommend using DEF USR & VARPTR unless you really do want to "pass values to and from Basic" and even then it's a bit of a headache. Having a BASIC loader is unnecessary unless you're using both BASIC and machine language together and especially want to have a single file (a BASIC...