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


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

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