Difference between revisions of "83Plus:Ports:4D"

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(Synopsis: 84+-only, duh)
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* Bit 0: Set if the D+ line is low.
 
* Bit 0: Set if the D+ line is low.
 
* Bit 1: Set if the D+ line is high.
 
* Bit 1: Set if the D+ line is high.
* Bit 2: Set if the D? line is low.
+
* Bit 2: Set if the D− line is low.
* Bit 3: Set if the D? line is high.
+
* Bit 3: Set if the D− line is high.
 
* Bit 4: Set if the ID line is low (i.e., a mini-A cable is connected.)
 
* Bit 4: Set if the ID line is low (i.e., a mini-A cable is connected.)
 
* Bit 5: Set if the ID line is high (i.e., no cable or a mini-B cable is connected.)
 
* Bit 5: Set if the ID line is high (i.e., no cable or a mini-B cable is connected.)
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== Comments ==
 
== Comments ==
This port allows you to see the actual states of the four (functional) USB lines at any given time.  This is mainly useful for checking the states of the ID and Vbus lines; while USB is active, the D+ and D? lines will change far too rapidly for you to get any useful information by polling this port.
+
This port allows you to see the actual states of the four (functional) USB lines at any given time.  This is mainly useful for checking the states of the ID and Vbus lines; while USB is active, the D+ and D− lines will change far too rapidly for you to get any useful information by polling this port.
  
 
I haven't tested what the actual cutoff voltages are, or whether there's any hysteresis.  There may be, but it's a good idea to be cautious anyway (e.g., if you're waiting for Vbus to go high, wait for a little while afterwards to be sure that it ''stays'' high.)
 
I haven't tested what the actual cutoff voltages are, or whether there's any hysteresis.  There may be, but it's a good idea to be cautious anyway (e.g., if you're waiting for Vbus to go high, wait for a little while afterwards to be sure that it ''stays'' high.)

Revision as of 15:12, 5 September 2010

Synopsis

Port Number: 4Dh

Function: USB Line State

This port reports the current states of the four functional USB lines.

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

Read Values

  • Bit 0: Set if the D+ line is low.
  • Bit 1: Set if the D+ line is high.
  • Bit 2: Set if the D− line is low.
  • Bit 3: Set if the D− line is high.
  • Bit 4: Set if the ID line is low (i.e., a mini-A cable is connected.)
  • Bit 5: Set if the ID line is high (i.e., no cable or a mini-B cable is connected.)
  • Bit 6: Set if the Vbus line is high.
  • Bit 7: Set if the Vbus line is low.

Write Values

  • No effect

Comments

This port allows you to see the actual states of the four (functional) USB lines at any given time. This is mainly useful for checking the states of the ID and Vbus lines; while USB is active, the D+ and D− lines will change far too rapidly for you to get any useful information by polling this port.

I haven't tested what the actual cutoff voltages are, or whether there's any hysteresis. There may be, but it's a good idea to be cautious anyway (e.g., if you're waiting for Vbus to go high, wait for a little while afterwards to be sure that it stays high.)