TI-92 Link Protocol Guide - Remote control/command

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Remote control/command

The TI-92's remote control ability is "silent," which means that the calculator does not need to be put in a special mode. The remote control ability can be utilized any time the calculator is ready to accept a keypress. Key codes : here.

Remote command:

The protocol used for sending a remote command is shown below.

Step | Direction | Packet
--- | --- | ---
1 |  |  |  | CMD
2 |  | ACK

The scancode of the key is sent in the last two bytes of the command. Scancodes are defined in the section B8 to B12 of the French TI-92 guidebook or p. 384 of the US TI-92 guidebook.

Example:

PC: | `09 87 31 00` | Command: Key <1>
TI: | `89 56 00 00` | Acknowledgement of command

If the calculator is put into the self test menu (<F5> + <diamond> + <(> + <s> from the home screen) then sent back to the home screen, then whenever a command result becomes available the calculator will send it through the link port as expression data. Each transmission from the calculator does not include a packet header or checksum but is terminated with 0xFF (see below).
Remote Control Mode:
The remote control mode can be activated either by pressing <F5> + <DIAMOND> + <(>+<R> or by sending this key sequence directly to the calculator via remote commands. In this mode, the calculator can receive key codes as if they have been typed on the keyboard and send the result via the link port.
To control the calculator, a scancode must be sent trough the link port in a command packet. After each scancode is received, the calculator replies with an FFh byte. Whenever a command result becomes available, the calculator will send it through the link port as expression data, followed by an FFh byte.
Example:

PC: | `09 87 31 00` | Command: <1>
TI: | `FF` | Acknowledgement of command
PC: | `09 87 2B 00` | Command: <+>
TI: | `FF` | Acknowledgement of command
PC: | `09 87 41 00` | Command: <a>
TI: | `FF` | Acknowledgement of command
PC: | `09 87 0D 00` | Command: <ENTER>
TI: | `FF` | Acknowledgement of command
| `41 2B 31 FF` | Reply with result "a+1"

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