83Plus:Ports:8F

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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:
    • Named MGC_M_DEVCTL_SESSION in the HDRC
    • Set if VBus is high. (Cutoff between 1.5 V and 3 V)
  • Bit 1:
    • Named MGC_M_DEVCTL_HR in the HDRC
    • Peripheral routines like this bit.
  • Bit 2:
    • Named MGC_M_DEVCTL_HM in the HDRC
    • Set if calculator is host.
  • Bit 3:
    • Named MGC_M_DEVCTL_VBUS in the HDRC
    • Reset if VBus is externally powered.
  • Bit 4:
    • Named MGC_M_DEVCTL_VBUS in the HDRC
    • Set if VBus is externally powered.
  • Bit 5:
    • Always 0
    • 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.
    • Named MGC_M_DEVCTL_FSDEV in the HDRC
    • Possibly actually indicates whether the bus is in low-speed or full-speed
  • Bit 7:
    • Named M_DEVCTL_BDEVICE in the HDRC
    • Set if we are B-device (i.e. peripheral). This can change if you're implementing USB OTG.

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.