ZX Spectrum TAP generator from machine code lists
Disk image created from a data storage tape formatted for the Commodore 64 (C64) or ZX Spectrum systems; contains an exact copy of the data from the tape in a single file; typically used for games or other types of applications.
A TAP file is simply one datablock or a group of 2 or more datablocks, one followed after the other. The TAP file may be empty. Then it has a size of 0 bytes. There's no real file size limit, like real tapes, TAP files can also contain huge amounts of data blocks.
A four possible types of TAP file we can found. For BASIC program, for Numeric and Alphanumeric array and, code or screen blocks. This utility not included support for BASIC program type file is focused only in a machine code or screen files.
For TAP files all header are like this below.
| Data body lenght (2 bytes) | Flag type (1 byte) | Data body for this header - n bytes |
|---|
In case below, machine code file is, 1300 00 xxxxxxxxxx .. xx
Where, FLAG byte can be:
-
00 --> Standard header
-
FF --> Data code block.
Example: HEADER (see below) | Data block lenght + 2 bytes | 0xFF | data block | checksum XOR
This header is 19 bytes [2 to 20]
| offset | Lenght | descripcion | Aditional information |
|---|---|---|---|
| 0 | 2 | Always 0x1300 | About 19 bytes for this header type, in little endian |
| 2 | 1 | Flag byte | is 0x00 for a standard rom file |
| 3 | 1 | Data type | For machine code is 0x03 |
| 4 | 10 | Name of file | Always are 10 fixes bytes. Null chars are filled with 0x20 |
| 14 | 2 | Data lenght | Litle endian data lenght |
| 16 | 2 | Start address | |
| 18 | 2 | Not used | 0x0080 (little Endian, 32768) |
| 20 | 1 | Checksum | XORed type checksum |
Example:
1300 00 03 4A45542D504143202020 0020 204E 0080 C9
\____/ \__/ \__/ \____________________/ \____/ \____/ \____/ \__/
| | | | | | | |
| | | | | | | Checksum
| | | | | | Reserver, 32768 (little endian)
| | | | | Start address
| | | | Data lenght
| | | Code name
| | Type code
| FLAG type
Always is 0x1300 --> 19 bytes (little endian)
NOTE: In the example above, data lenght is 2000h --> 8192 bytes (in little endian is 0x0020)
For start address is 4E20h --> 20000 (in little endian is 0x204E)
This case is similar to the previous case (machine code header) but:
- Data lenght always is, 6912 bytes
- Starting address is, 16384 (video RAM)
Then, for example, 1300 00 03 xxxx .. xx 001B 0040 0080 xx
A TAP file is composed for a header and data block, with checksum on each case.