TI-73 Link Protocol Guide v1.0 - Silent Variable Transfers

"Silent Linking" is a capability that Texas Instruments built into the TI-83, TI-73, 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=0x19 (see note under Type ID's for variable header format)
2				ACK
3				DATA: 2-byte free memory count (little-endian)
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

Example:

PC:	07 A2 0B 00 00 00 19 00 00 00 00 00 00 00 00 19 00	Directory request
TI:	74 56 00 00	Acknowledgement of request
	74 15 02 00 66 5B C1 00	Data: 23398 (5B66h) bytes of free memory
PC:	07 56 00 00	Acknowledgement of data
TI:	74 06 0B 00 09 00 00 41 00 00 00 00 00 00 00 4A 00	Variable Header: Real Number "A"
PC:	07 56 00 00	Acknowledgement of variable header
TI:	74 06 0B 00 09 00 00 42 00 00 00 00 00 00 00 CB 00	Variable Header: Real Number "B" which is archived
PC:	07 56 00 00	Acknowledgement of variable header
TI:	74 92 00 00	No more variables
PC:	07 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:	07 A2 0B 00 00 00 01 5D 01 00 00 00 00 00 00 4A 00	Request List "L1"
TI:	74 56 00 00	Acknowledgement of request
	74 06 0B 00 02 00 01 5D 01 00 00 00 00 00 00 61 00	Variable Header: List "L1"
PC:	07 56 00 00	Acknowledgement of variable header
	07 09 00 00	Clear to send variable
TI:	74 56 00 00	Acknowledgement of CTS
	74 15 02 00 00 00 00 00	Variable data
PC:	07 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

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:	07 C9 0B 00 02 00 01 5D 01 00 00 00 00 00 00 61 00	Request to send List "L1"
TI:	74 56 00 00	Acknowledgement of request
	74 09 00 00	Clear to send variable
PC:	07 56 00 00	Acknowledgement of CTS
	07 15 02 00 00 00 00 00	Variable data
TI:	74 56 00 00	Acknowledgement of data
PC:	07 C9 0B 00 09 00 00 42 00 00 00 00 00 00 00 4B 00	Request to send Real Number "B"
TI:	74 56 00 00	Acknowledgement of request
	74 36 01 00 03 03 00	Out of memory
PC:	07 56 00 00	Acknowledgement of out of memory

Manual Transfers

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