TI-86 Link Protocol Guide v1.0 - Silent Variable Transfers

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Silent Variable Transfers

"Silent Linking" is a capability that Texas Instruments built into the TI-83, TI-83+, TI-86, TI-89, TI-92 and TI-92+. It enables the calculator to transfer data to and from a computer without any special preparation required on the calculator end. The only drawback to the silent linking method is that when using this protocol, the calculator will automatically overwrite any data in a variable that has the same name as one being sent to it. Any program that incorporates silent linking must check for this; otherwise data may be lost.

Because silent linking protocols are one-sided (i.e. the user interaction is solely on the computer), there are three different transfer sequences required. First a directory listing must be downloaded from the calculator in order to choose the variables to transfer or to check for duplicate names and out-of-memory conditions. Then, if variables are to be downloaded, a variable request action must be initiated by the computer. Finally, if variables are to be uploaded, a request-to-send action must be sent by the computer.

#### Directory Listing

A directory listing is a list of all user variables in the calculator's memory and a number specifying how many bytes of free memory are left.

The protocol for requesting a directory listing is shown below. For information on packet formats, click here.

Step | Direction | Packet
--- | --- | ---
1 |  |  |  | REQ with data type=0x15 (see note under Type ID's for variable header format)
2 |  | ACK
3 |  | DATA (3-byte free memory count - see format below)
4 |  | ACK
|  | (Repeat steps 5 and 6 for all user variables in the calculator's memory)
5 |  | VAR (with padded variable header) - one entry
6 |  | ACK
7 |  | EOT
8 |  | ACK

The data section of the transfer is three bytes long and takes the following format:

Offset | Length | Description
--- | --- | ---
0 | 1 byte | Most significant 8 bits of the free memory count
1 | 2 bytes | Least significant 16 bits of the free memory count (little-endian)

Example:

PC: | `06 A2 05 00` `00 00 15 00 00 16 00` | Directory request
TI: | `86 56 05 00` | Acknowledgement of request
| `86 15 03 00` `01 65 15 7B 00` | Data: 71013 (11565h) bytes of free memory
PC: | `06 56 00 00` | Acknowledgement of data
TI: | `86 06 0C 00` `02 00 04 05 79 53 74 61 74 20 20 20` `80 02` | Variable Header: Real Number "xStat"
PC: | `06 56 00 00` | Acknowledgement of variable header
TI: | `86 06 05 00` `02 00 04 05 7A 53 74 61 74 20 20 20 81 02` | Variable Header: Real Number "yStat"
PC: | `06 56 00 00` | Acknowledgement of variable header
TI: | `86 92 00 00` | No more variables
PC: | `06 56 00 00` | Acknowledgement of EOT

#### Requesting a Variable

The protocol for requesting and receiving a variable from the calculator is shown below.

Step | Direction | Packet
--- | --- | ---
1 |  |  |  | REQ with expected header
2 |  | ACK (see note below)
3 |  | VAR with actual header
4 |  | ACK
5 |  | CTS
6 |  | ACK
7 |  | DATA
8 |  | ACK

Note: If the requested variable does not exist, the calculator will send an EXIT packet after step 2, to which the computer will respond with an ACK packet. This would be the end of the transfer.

As with manual transfers, the data section contains the variable data. For information on variable formats, click here.

Example:

PC: | `06 A2 0C 00` `02 00 04 05 79 53 74 61 74 20 20 20 80 02` | Request Unknown "xStat"
TI: | `86 56 0C 00` | Acknowledgement of request
| `86 06 05 00` `0A 00 00 01 41 4C 00` | Variable Header: Real Number "A"
PC: | `06 56 00 00` | Acknowledgement of variable header
| `06 09 00 00` | Clear to send variable
TI: | `86 56 00 00` | Acknowledgement of CTS
| `86 15 0A 00` `00 00 FC 62 83 18 53 07 18 00 5B 02` | Variable data: "6.28318530718"
PC: | `06 56 00 00` | Acknowledgement of variable data

#### Sending a Variable

The protocol for sending a variable to the calculator is shown below.

Step | Direction | Packet
--- | --- | ---
1 |  |  |  | RTS
2 |  | ACK
3 |  | CTS or SKIP/EXIT (see note below)
4 |  | ACK
5 |  | DATA
6 |  | ACK
7 |  | EOT

Note: If the calculator sends a SKIP/EXIT packet in step 3, it does not have enough free memory to accomodate the variable. In this case, step 4 will be the end of the transfer.

Again, the data section contains the variable data.

Examples:

PC: | `06 C9 0C 00` `0A 00 00 01 41 20 20 20 20 20 20 20 2C 01` | Request to send Real Number "A"
TI: | `86 56 0C 00` | Acknowledgement of request
| `86 09 0C 00` | Clear to send variable
PC: | `06 56 00 00` | Acknowledgement of CTS
| `06 15 0A 00` `00 00 FC 62 83 18 53 07 18 00 5B 02` | Variable data: "6.28318530718"
TI: | `86 56 0A 00` | Acknowledgement of data
PC: | `06 92 00 00` | End Of Transmission
PC: | `06 C9 0C 00` `0A 00 00 01 42 20 20 20 20 20 20 20 2D 01` | Request to send Real Number "B"
TI: | `86 56 00 00` | Acknowledgement of request
| `86 36 01 00` `03 03 00` | Out of memory
PC: | `06 56 00 00` | Acknowledgement of out of memory

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Site maintained by Romain Liévin (roms@lpg.ticalc.org) and Tim Singer (tsinger@gladstone.uoregon.edu)