83Plus:Ports:4A

This port only exists on the the TI-84 Plus and the TI-84 Plus Silver Edition. On the standard TI-83 Plus, it acts as a shadow of port 02. On the TI-83 Plus Silver Edition, this port has no effect.

Synopsis

Port Number: 4A

Function: Pull-up/down Control

Controls low-level USB pull-up/pull-down resistors. Using this port, you can control the D− USB line. The USB controller doesn't even have to be powered.

Read Values

• Bit 0: Set if 2 and 6 of port 54 are set, 3 of port 4C is set, and VBus is high.
• Bit 1: Set if not connected to computer. Flashes when talking to computer.
• Bit 2: Reset if 2 and 6 of port 54 are set, 3 of port 4C is set, and VBus is high.
• Bit 3: If set, D− is forced high. Max 0.79 mA.
• Bit 4: Only significant if bit 3 is set. If this is set, D− gets extra power. Max total 1.52 mA.
• Bit 5: Reset means D− is getting 0.05 V at 15μA.
• Bits 6-7: No function

Write Values

• Bits 0-2: Read only
• Bit 3: Pull-up switch on D-, set to enable; forces D− high. Max output: 0.79 mA.
• Bit 4: Some kind of additional pull-up? Setting this give D− extra power. Max total output 1.52 mA.
• Bit 5: Pull-down switch, should be left set; resetting this gives D− 0.05 V at 15μA.
• Bits 6-7: No function

Comments

If you don't like USB protocol, you could try to use this port for communication, or for sound. Anyways, when you are done, output 20h. If you don't, USB communications probably won't work.