TI-89 Link Protocol Guide - System Backup Transfers

System Backup Transfers

A System Backup is one large transmission containing all user-modifiable data in the calculator. The file format that the TI-89 Graph Link software uses can be found in the file formats section of this documentation.

System backups must be transferred silently. Silent transfers can only be done between a computer and a calculator, and require that the computer make the request or request-to-send.

Requesting a Backup

Indeed, receiving a backup is a group of all variables of the calculator. So, it is necessary to make a directory list in order to have the list of variables to receive.

Sending a Backup

Indeed, sending a backup is a group of all variables of the calculator. There is just a special block transmitted before sending the group of variables.

The protocol for silently sending the special block is shown below:
Step Direction Packet
1 
Computer
===>
Calculator
 VAR with send-style backup header.
2 
<===
 ACK
3 
<===
 CTS
4 
===>
 ACK
5 
===>
 EOT
6 
<===
 ACK

Next, all variables are sent according to the 'Sending a variable' operation with one important exception: the type field is equal to either 1Dh (none), 26h (locked) or 27h (archived), independantly of the variable type.
 
Step Direction Packet
1 
Computer
===>
Calculator
 RTS (specifing the size with the extra four bytes) and with a particular type (1Dh, 26h or 27h)
2 
<===
 ACK
3 
<===
 CTS or SKIP/EXIT (see note below)
4 
===>
 ACK
5 
===>
 DATA
6 
<===
 ACK
7 
===>
 EOT - if there are several variables to transmit, steps 7 and 8 can be skipped until the last variable.
8 
<===
 ACK

Example (PC sending backup from TI):
PC: 08 06 0A 00 00 00 00 00 00 1D 04 6D 61 69 6E C6 01 Variable header: Backup ("main")
TI: 98 56 00 00 Acknowledgement of header
  98 09 00 00 Clear To Send
PC: 08 56 00 00 Acknowledgement of CTS
  08 92 00 00 End of transmission
TI: 98 56 00 00 Acknowledgement of data
. . .
. . .
. . .
PC: 09 C9 0D 00 0F 00 00 00 1D 06 6D 61 69 6E 5C 66 01 9A 02 Variable header: "main/f" (none)
TI: 98 56 00 00 Acknowledgement of header
  98 09 00 00 Clear To Send
PC: 08 56 00 00 Acknowledgement of CTS
  08 15 13 00 00 00 00 00 00 0D E9 02 01 1F 08 F0 93 E5 08 00 00 00 DC 6C 04 Variable content
TI: 98 56 00 00 Acknowledgement of data
PC: 08 92 00 00 End of transmission
TI: 98 56 00 00 Acknowledgement of EOT
. . .
. . .
. . .
PC: 08 C9 10 00 06 00 00 00 1D 09 6D 79 5F 64 69 72 5C 73 31 00 B0 03 Variable header: "my_dir/s1"
 
...
  
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