#target .P, .81 and .P81

this format is not yet well tested. Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifIf there are problems please send an email to Kio.

This creates a tape file for use with a ZX81 emulator. The tape file will be loaded to the ram start + 9 at address $4009.

"p" can be used instead of "81". This will create a target file with extension "p" or "81" respectively, which are fully identical. ".p81" files also include the program name which must be written using the ZX81 character Pseudo instructions: defl, set and '='
Labels: SETset.

Code may be stored in one or more Assembler directives: #code
Including C Source Files: #code#code segments. However, the first segment must be at least 0x403B - 0x4009 bytes long and contain the system variables. (except for the first 9 bytes which are not saved.)

Assembler directives: #target
Including C Source Files: #target#target 81
#charset ZX81
Assembler directives: #code
Including C Source Files: #code#code <name>,<start>,<len>
    ...

or:

Assembler directives: #target
Including C Source Files: #target#target p81
#charset ZX81
Assembler directives: #code
Including C Source Files: #code#code   _PROGNAME
    dm  "progname" | $80        ; zasm converts the characters to charset ZX81!
Assembler directives: #code
Including C Source Files: #code#code   _RAM, 0x4009, _ram_end - 0x4009
    ...

See the ZX81 .p template file: template_p.asm

The tape data is always loaded to $4009, so this is the only choice for the <start> address in the Assembler directives: #code
Including C Source Files: #code#code directive. The <size> may be any value up to a maximum of $C000 minus $09, but most ZX81 had at most 16 kB ram Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifif extended with an external memory expansion, only 1 kB Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifif none. (The TS1000 had whoopy 2k!)

The ram starts with system variables from $4009 to $403C, which must be Pseudo instructions: defl, set and '='
Labels: SETset to proper values. The variable E_LINE at the address $4014, which contains the Pseudo instructions: end, .end
8080 pseudo instructions: ENDend of ram address, is checked by the assembler.

This file also contains the screen file, which basically means, that the video memory must contain 25 HALT opcodes Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifif the file was saved in SLOW mode.

Here are few important variables:

$4014   defines the Pseudo instructions: end, .end
8080 pseudo instructions: ENDend address (used to calculate the file length)
$4029   points to the next executed (autostarted) BASIC line
$403B   bit 6 indicates Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifif program runs in SLOW or FAST mode
$403C++ may be misused for whatever purpose

zasm has a convenient assembler directive to translate from the ascii (or utf-8) characters in your source file to the non-ascii character Pseudo instructions: defl, set and '='
Labels: SETset of the ZX81:

#charset ZX81

You can include c sources in your assembler file, but there are two pitfalls:

You can use the character Pseudo instructions: defl, set and '='
Labels: SETset translation of zasm to translate strings in your c source as well. But unluckily character literals are not exported as character literals by the c compiler sdcc but as their ascii code and zasm has no chance to detect this. So character literals in your c source are not translated.

Second, character 0x00 is used in c sources as a string Pseudo instructions: end, .end
8080 pseudo instructions: ENDend indicator, but it is also a valid character for the ZX81: the space. So you'll have to think of a way to work around this problem.