83Plus:Ports:8F

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 07. On the TI-83 Plus Silver Edition, this port has no effect.

Synopsis

Port Number: 8F

Equivalent HDRC port: Possibly MGC_O_HDRC_DEVCTL (0x60)

Function: VBus Control

Using this port, you can control the VBus line and see its status.

Read Values

• Bit 0:
  • Set if VBus is high. (Cutoff between 1.5 V and 3 V)
  • Possibly named MGC_M_DEVCTL_SESSION in the HDRC
• Bit 1:
  • Unknown. Peripheral routines like this bit.
  • Possibly named MGC_M_DEVCTL_HR in the HDRC
• Bit 2:
  • Set if calculator is host.
  • Possibly named MGC_M_DEVCTL_HM in the HDRC
• Bit 3:
  • Reset if VBus is externally powered.
  • Possibly named MGC_M_DEVCTL_VBUS in the HDRC
• Bit 4:
  • Set if VBus is externally powered.
  • Possibly named MGC_M_DEVCTL_VBUS in the HDRC
• Bit 5:
  • Always 0
  • Possibly named MGC_M_DEVCTL_LSDEV in the HDRC
  • Possibly actually indicates whether the bus is in low-speed or full-speed
• Bit 6:
  • Set if calculator is successfully hosting a device. It gets set when the device turns on.
  • Possibly named MGC_M_DEVCTL_FSDEV in the HDRC
  • Possibly actually indicates whether the bus is in low-speed or full-speed
• Bit 7:
  • Reset if A-Type cable is currently inserted.
  • Possibly named M_DEVCTL_BDEVICE in the HDRC

Write Values

• Bit 0: Set to power VBus. This will only stick if the USB controller ports are set up correctly. Most notably port 4C and port 54.
• Bit 2: Unknown. Peripheral routines sometimes set this.
• Bits 3-7: No effect

Comments

If VBus is internally powered and you short circuit it, it will power down.

Bit 6 is pretty strange, it's not as simple as VBus high, or even VBus supplying power. I lit an LED drawing 30 mA off of VBus and port 6 stayed off. But .5 sec after I plug in a USB device, it sets itself.