Z88DK — Mixing C Asm — How to

Some incredibly short notes to remind me how to mix C and ASM together in the same project using Z88DK for my RC2014. I have yet to work out how to pass parameters or return data.

Some of this information came from the RC2014 Z88DK wiki page.

The C File

You need this code at the top to set ORG to 0x8000

#pragma output CRT_ORG_CODE = 0x8000
#pragma output CRT_REGISTER_SP = 0xFC00

And the Asm function you want to call needs an extern like this

extern void oled_init();

The ASM File

The top of the ASM file needs to look like this. I found this mentioned in this example file.

SECTION code_user
PUBLIC _oled_init

Followed by the function

_oled_init:
    call reset
    ld HL, SEQUENCE
    ... etc ...

They need the leading underscores, I don’t yet know why.

Compiling

Compiling is like this

zcc +rc2014 -subtype=basic -clib=sdcc_iy -v -m -SO3 --max-allocs-per-node200000 --c-code-in-asm --list @sources.lst -o whatever -create-app

• +rc2014 for the RC2014
• -subtype=basic for the BASIC or SCM ROM
• -clib=sdcc_iy for stdio
• -SO3 –max-allocs-per-node200000 is optimisation stuff
• –c-code-in-asm does something that can be removed
• @sources.lst is a file containing each source file to be compiled
• -create-app creates an Intel HEX dump, paste it into the RC2014 terminal

Here’s my RC2014 enabling the Quazar OLED Interface using ASM routines, but called from a C program