Spectrum game disassembly toolkit

Control freak

@remote control

SkoolKit 6.3 has been released. Copies are, as you read this, rolling off the assembly lines in the usual locations: the download page, the Python Package Index, the Ubuntu PPA, and the Fedora copr repo.

Arriving only 7 weeks after 6.2, but still packing one of the largest changelogs in SkoolKit history, this new version of your favourite Spectrum disassembly toolkit brings 4 new ASM directives, 3 enhancements to existing ASM directives, 2 new command options, 3 bug fixes, and a whole bunch of other stuff. Given this embarrassment of riches, it’s difficult to know where to start.

So let’s start with the new ASM directives. The first three are @defb, @defs and @defw, which mimic DEFB, DEFS and DEFW statements without having to appear anywhere in the memory map, and also override the contents of the memory snapshot. Now just a minute, you may be thinking. Isn’t the purpose of these directives already served by data definition entries? To which I would respond: Yes, but hold on. The @def* directives are no mere cheap imitation of ‘d’ blocks. Unlike ‘d’ blocks, they can be preserved in a control file, and will override the contents of the snapshot when is reading them from a control file.

While you ponder the significance of that nugget of info, let me introduce the fourth new ASM directive: @remote. It creates a remote entry that enables JR, JP and CALL instructions to hyperlink across skool files. By now, you might have guessed the main advantage of using @remote over the traditional ‘r’ block. Yes, it can be preserved in a control file. Clearly, the ability to be preserved in a control file is a big theme in 6.3. (SkoolKit historians may also like to note that @remote is uncannily similar to the !refs directive in SkoolKit 1.x.)

Still on the subject of ASM directives, the @label directive can (and should) now be used to emulate the (now redundant) @nolabel directive by providing a blank label: @label=. Also, the @org directive no longer requires an address: it defaults to the address of the next instruction, as you might expect. And finally, the @assemble directive has picked up two new abilities: it can specify what to convert in HTML mode and ASM mode separately, and switch off conversion entirely. Conversion is also now switched off entirely by default in ASM mode, which means should run a little faster.

Let’s finish up with some commentary on the new command options. First, now has a --poke option, which can be useful for POKEing the system variables in a binary file that doesn’t provide its own. And has a --user-agent option for setting the user agent when making HTTP requests. By default, sends no User-Agent header, but if you run into a website that expects one, --user-agent is your friend.

So there we have it. For details on all the other new features and fixes, I advise you to take a gander at the changelog. After that, I suggest you rip out all the ‘d’ blocks, ‘r’ blocks, @nolabel directives and addressful @org directives from your skool files, and stomp them into the dust before providing the 6.3-style replacements. Good times!

In your 0xFACE

@keep it real

SkoolKit 6.2 has been released. As always, copies are available from the download page, the Python Package Index, the Ubuntu PPA, and the Fedora copr repo.

Back in SkoolKit 2.0.6, you may remember, support for hexadecimal numbers began to appear, with control files being the first to allow numbers in either base 10 or base 16. Since then, hexadecimal has established a firm foothold as a first class number base in SkoolKit’s feature set: 2.1.1 saw and gain the ability to convert a disassembly to hexadecimal, and in 4.3 it became possible to render address anchors and disassembly page filenames in hexadecimal. Today, 6.2 continues that tradition by adding support for hexadecimal numbers to SkoolKit’s command options wherever an address, byte, length, step, offset or range limit value is expected. So, for example, you can now do stuff like this:

$ --start 0x8000 --end 0xf800 game.z80 > game.skool
$ --poke 0x9f43,0xff --reg pc=0xc33f game.z80 hacked.z80

In other command-related news, has picked up the --reg and --state options (for setting the value of a register or hardware state attribute). And can now read a binary (raw memory) file when the --binary option is used, and with a specific origin address when the --org option is used. And, and all now sport the --show-config option (for showing configuration parameter values).

Enough about commands. Among the ASM directives, @nolabel is now processed in HTML mode. (This change should have been made back in SkoolKit 3.4 - when support was added for labels in HTML mode - but better late than never.) And the @keep directive is now also applied to instructions that have been replaced by an @isub, @ssub or @rsub directive. This change could affect the output of on an existing disassembly, preventing the substitution of a label for an address in @isub, @ssub or @rsub mode. For example, in SkoolKit 6.1 and earlier, the instruction at 31898 below would be replaced by LD DE,31861%256*256+62 in @ssub mode, and then ‘31861’ would be replaced by a label (if there is one) because the @keep directive is not applied in @ssub mode:

@ssub=LD DE,31861%256*256+62
31898 LD DE,30014

But in 6.2, this @keep directive (originally intended to prevent a label from being substituted for the value ‘30014’) is applied in @ssub mode, and prevents a label from being substituted for ‘31861’. The fix is to use the @keep directive’s new ability to specify the values to keep:

@ssub=LD DE,31861%256*256+62
31898 LD DE,30014

Now, in @ssub mode, ‘31861’ will be replaced by a label, as desired.

And that’s it for the main new features in this release. For details of all the other changes, the changelog is at your service.

Horace and the disassembly

Arriving just in time for Christmas, a new disassembly has just been added to the gallery here at The complete Hungry Horace RAM disassembly.

This disassembly began life as a bare-bones control file back in SkoolKit 4.1.1 (version 20140920), and was recently ‘completed’ by adding annotations to all the routines, data blocks and text blocks. There are no ‘Bugs’, ‘Pokes’ or ‘Trivia’ pages yet, but you can expect them to appear in the next update.

Of course, the disassembly is also available in downloadable form, and a hexadecimal version can be browsed at GitHub too. There’s never been a better time to find out what makes Horace and the park guards tick!