TI-85 Link Protocol Guide v1.0 - File formats

The TI-85 Graph Link software stores variables in several types of files. Single variables are stored in files that have an extension that corresponds with their type. Groups of variables are stored in files with the extension ".85g". However, all of these file types have a common format (excepting backups).

The different file types and contents that the TI-86 Graph Link software can read and write are shown below.

Extension	Description
.85b	TI-85 system backup
.85c	TI-85 complex number
.85d	TI-85 GDB (function, polar, parametric or differential equation)
.85e	TI-85 equation
.85g	Multiple TI-85 variables of varying types (group)
.85i	TI-85 picture (image)
.85k	TI-85 constant (real or complex)
.85l	TI-85 list (real or complex)
.85m	TI-85 matrix (real or complex)
.85n	TI-85 real number
.85p	TI-85 program
.85r	TI-85 range (Func, Pol, Param, DifEq or ZSTO)
.85s	TI-85 string
.85v	TI-85 vector

The TI-85 variable file format

The TI-85 variable file format has two parts: a header and several variable entries.

The header appears at the beginning of the file and takes the following format:
Note - All 2-byte integers are stored little-endian Intel-style (least significant byte first).

Offset	Length	Description
0	8 bytes	8-character signature. The signature is always "**TI85**".
8	3 bytes	3-byte further signature. These three bytes always contain {1Ah, 0Ch, 00h} = {26, 12, 0}
11 (Bh)	42 (2Ah) bytes	Comment. The comment is either zero-terminated or padded on the right with space characters.
53 (35h)	2 bytes	Length, in bytes, of the data section of the file. This number should be 57 (39h) bytes less than the file size.
55 (37h)	n bytes	Data section - consists of a number of variable entries (described below).
55 (37h)+n	2 bytes	File checksum. This is the lower 16 bits of the sum of all bytes in the data section.

Each variable entry follows this format:

Offset	Length	Description
0	2 bytes	Offset to data length: 6 plus the length, in characters, of the variable name.
2	2 bytes	Length, in bytes, of the variable data.
4	1 byte	variable type ID byte (see variable type ID's)
5	1 byte	Length, in characters, of the variable name
6	m bytes	Variable name (not zero-terminated).
6+m	2 bytes	Length, in bytes, of the variable data (This is a copy of the value in offset 2).
8+m	n bytes	Variable data. Click here for variable data formats.

The TI-85 backup file format

Most link programs allow a user to download and save system backups with the extension ".85b".

Here is the format for backup files:

Offset	Length	Description
0	8 bytes	8-character signature. The signature is always "**TI85**".
8	3 bytes	3-byte further signature. These three bytes always contain {1Ah, 0Ch, 00h} = {26, 12, 0}
11 (Bh)	42 (2Ah) bytes	Comment. The comment is either zero-terminated or padded on the right with space characters.
53 (35h)	2 bytes	Length, in bytes, of the backup header and the data sections. This number should be 17 (11h) bytes more than the sum of the lengths of the three data sections as reported in the backup header.
55 (37h)	11 bytes	The backup header (format described below).
66 (42h)	2 bytes	Length, in bytes, of the firstdata section
68 (44h)	x bytes	First data section.
68 (44h)+x	2 bytes	Length, in bytes, of the second data section
70 (46h)+x	y bytes	Second data section.
70 (46h)+x+y	2 bytes	Length, in bytes, of the third data section
72 (48h)+x+y	z bytes	Third data section
72 (48h)+x+y+z	2 bytes	Checksum. This is the lower 16 bits of the sum of all bytes in the backup header and data sections.

The backup header has this format:

Offset	Length	Description
0	2 bytes	Offset to data length: Always has a value of 9.
2	2 bytes	Length, in bytes, of the first data section.
4	1 byte	Type ID: Always has a value of 1Dh.
5	2 bytes	Length, in bytes, of the second data section.
7	2 bytes	Length, in bytes, of the third data section.
9	2 bytes	Memory address of the second data section

Variable Formats

Table of Contents

Tokens and Characters