Tape Loaders

Notes on various program loaders

1 TAP

1.1 BASIC Loader

1 - TAP

Example code to load a machine code program in TAP format

A .TAP file is a simple image format used to represent data saved to tape. It's a simple image format which can be generated by some assemblers like zasm.

Now we have a simple BASIC loader which generates a .TAP file. This is effectively a simple BASIC program which when run loads the next file on the tape into memory at address 24000 0x5DC0 and then executes the machine code at that same address.

Hello World Example

For this example we will write a simple machine code program which writes Hello World to the screen.

1wget https://area51.dev/sinclair/asm/loaders/tap/loader.tap
2wget https://area51.dev/sinclair/asm/loaders/tap/helloworld.z80
3zasm helloworld.z80
4cat loader.tap helloworld.tap > tape.tap

The commands do the following:

Download loader.tap which is the precompiled loader. The source is viewable here along with how to compile it yourself.
Download helloworld.z80 which is the source shown below.
Compiles the source generating helloworld.tap.
Concatenates both tap files to generate our final tape.tap file.

Links to the required files are available in the Resources panel at the top right of this page including a precompiled helloworld.tap file.

Running the example

If no errors occurred you can run it with the fuse emulator:

1fuse tape.tap

You should then see something like this screenshot.

The first line visible is from the boot loader as it loaded the file in helloworld.tap.

The second line is the output of the source below.

helloworld.z80 source

; ***************************************************************************
; Hello world example showing how to use the TAP format and our simple
; BASIC boot loader that has been recompiled into TAP format.
;
; Author: Peter Mount, Area51.dev & Contributors
; URL: https://area51.dev/sinclair/asm/loaders/tap/
; ***************************************************************************

; for zasm we need to tell it to generate a tap file
#target tap

; code_start will be where our code will be compiled to
code_start equ 24000

; ***************************************************************************
; Header block containing the block name and the size of the machine code
; ***************************************************************************

#code CODE_HEADER,0,17,0
        defb    3                       ; Indicates binary data
        defb    "helloworld"            ; the block name, 10 bytes long
        defw    code_end-code_start     ; length of data block which follows
        defw    code_start              ; default location for the data
        defw    0                       ; unused

; ***************************************************************************
; Data block containing a actual machine code program:
;
; Here we simply print the "Hello World!" message to the screen.
; ***************************************************************************

#code CODE_DATA, code_start,*,0xff

; This is the code_start address 24000 0x5DC0
        ld      a,2                     ; set print channel to Screen:
        call    0x1601

        ld      hl,msg                  ; message start address
loop:   ld      a,(hl)                  ; get next byte
        and     a                       ; check for null
        ret     z                       ; stop when we get a null
        inc     hl                      ; move to next character
        rst     2                       ; print the character
        jr      loop                    ; jump back to the loop

msg:    dm      13, "Hello World!", 13, 0

; End of code marker needed for the CODE_HEADER
code_end:

; Anything after this point will not be included in the .tap file

1.1 - BASIC Loader

BASIC .TAP loader

This shows the source for the BASIC .TAP loader for use with the zasm assembler.

To compile run the following commands in a Linux shell to download the sources and compile the loader:

1wget https://area51.dev/sinclair/spectrum/reference/include/zasm/headers.z80
2wget https://area51.dev/sinclair/asm/loaders/tap/loader.z80
3zasm loader.z80

The commands do the following:

Download headers.z80 which contains the definitions for the Spectrum BASIC tokens we require.
Download loader.z80 which is the source shown below.
Compiles our loader generating loader.tap.

The generated loader.tap can now be used with your own .TAP file as long as it loads at address 24000 and its entry point is also at that same address.

All you need to do is concatenate both .TAP files with loader.tap first. The Hello World example shows how this is done.

Links to the required files are shown in the resources panel at the top right of this page.