83Plus:Ports:4D - Revision history

Thepenguin77 at 04:01, 28 October 2011

2011-10-28T04:01:43Z

Thepenguin77 at 03:13, 4 June 2011

2011-06-04T03:13:34Z

Thepenguin77 at 03:06, 4 June 2011

2011-06-04T03:06:41Z

FloppusMaximus at 22:12, 5 September 2010

2010-09-05T22:12:47Z

FloppusMaximus: /* Synopsis */ 84+-only, duh

2010-09-05T21:34:45Z

‎Synopsis: 84+-only, duh

FloppusMaximus: Documenting the USB ports. Starting with the easy ones.

2010-09-05T21:31:08Z

Documenting the USB ports. Starting with the easy ones.

New page

[[Category:83Plus:Ports:By Address|4D - USB Line State]] [[Category:83Plus:Ports:By Name|USB Line State]]
== Synopsis ==
'''Port Number:''' 4Dh

'''Function:''' USB Line State

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

=== 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.)

← Older revision		Revision as of 21:34, 5 September 2010
Line 6:		Line 6:

	This port reports the current states of the four functional USB lines.		This port reports the current states of the four functional USB lines.
		+
		+	{{84P-Only Port\|05}}

	=== Read Values ===		=== Read Values ===

@@ Line 1: / Line 1: @@
 [[Category:83Plus:Ports:By Address|4D - USB Line State]] [[Category:83Plus:Ports:By Name|USB Line State]]
 == Synopsis ==
 '''Port Number:''' 4Dh
@@ Line 7: / Line 8: @@
 This port reports the current states of the four functional USB lines.
-{{84P-Only Port|05}}
 === Read Values ===

@@ Line 16: / Line 16: @@
 * 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'''. (Cutoff between 3 and 4.5)
+* Bit 6: Set if the Vbus line is '''high'''. Electricity actually has to be moving, it can't just be powered. (Cutoff between 3 and 4.5)
 * Bit 7: Set if the Vbus line is '''low'''.

@@ Line 10: / Line 10: @@
 === Read Values ===
-* Bit 0: Set if the D+ line is low.
+* Bit 0: Reset if the D+ line is high or if 2 and 6 of [[83Plus:Ports:54|port 54]] are set, 3 of [[83Plus:Ports:4C|port 4C]] is set, and VBus is high.
-* Bit 1: Set if the D+ line is high.
+* Bit 1: Set if the D+ line is high or if 2 and 6 of [[83Plus:Ports:54|port 54]] are set, 3 of [[83Plus:Ports:4C|port 4C]] is set, and VBus is high. (Cutoff for both between 1.5 V and 3 V)
 * Bit 2: Set if the D&#8722; line is low.
-* Bit 3: Set if the D&#8722; line is high.
+* Bit 3: Set if the D&#8722; line is high. (Cutoff between 1.5 V and 3 V)
 * 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 6: Set if the Vbus line is '''high'''. (Cutoff between 3 and 4.5)
 * Bit 7: Set if the Vbus line is '''low'''.

@@ Line 12: / Line 12: @@
 * 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 2: Set if the D&#8722; line is low.
-* Bit 3: Set if the D? line is high.
+* Bit 3: Set if the D&#8722; 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.)
@@ Line 23: / Line 23: @@
 == 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&#8722; 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.)