83Plus:Ports:56 - Revision history

Thepenguin77 at 04:15, 28 October 2011

2011-10-28T04:15:14Z

FloppusMaximus at 22:13, 5 September 2010

2010-09-05T22:13:11Z

FloppusMaximus: Port 56 - line events

2010-09-05T21:45:01Z

Port 56 - line events

New page

[[Category:83Plus:Ports:By Address|56 - USB Line Events]] [[Category:83Plus:Ports:By Name|USB Line Events]]
== Synopsis ==
'''Port Number:''' 56h

'''Function:''' USB Line Events

This port reports which, if any, USB line interrupts have occurred.

{{84P-Only Port|16}}

=== Read Values ===
* Bit 0: Set if the D+ line has gone low.
* Bit 1: Set if the D+ line has gone high.
* Bit 2: Set if the D? line has gone low.
* Bit 3: Set if the D? line has gone high.
* Bit 4: Set if the ID line has gone low.
* Bit 5: Set if the ID line has gone high.
* Bit 6: Set if the Vbus line has gone '''high'''.
* Bit 7: Set if the Vbus line has gone '''low'''.

=== Write Values ===
* No effect

== Comments ==
This port reports when an interrupt has occurred due to one of the USB lines changing from high to low, or low to high.

Normally, only a subset of the above events are actually enabled; [[83Plus:Ports:57|port 57]] controls which. For instance, when the calculator starts up, the OS initially monitors only the ID-low and Vbus-high events (the former to notify it when an A-cable is plugged in, the latter to notify it when a powered B-cable is plugged in.)

To acknowledge a USB line interrupt, clear the corresponding bit of [[83Plus:Ports:57|port 57]] (and then set the bit again, if you want to get another interrupt the next time it happens.) If a line has changed state twice, and you've enabled both events, both bits will be set. The only way for bits in this port to be cleared is by clearing the corresponding bit of port 57.

(If you want to see the ''current'' states of the USB lines, see [[83Plus:Ports:4D|port 4D]].)

@@ Line 1: / Line 1: @@
 [[Category:83Plus:Ports:By Address|56 - USB Line Events]] [[Category:83Plus:Ports:By Name|USB Line Events]]
 == Synopsis ==
 '''Port Number:''' 56h
@@ Line 6: / Line 7: @@
 This port reports which, if any, USB line interrupts have occurred.
 === Read Values ===

@@ Line 12: / Line 12: @@
 * Bit 0: Set if the D+ line has gone low.
 * Bit 1: Set if the D+ line has gone high.
-* Bit 2: Set if the D? line has gone low.
+* Bit 2: Set if the D&#8722; line has gone low.
-* Bit 3: Set if the D? line has gone high.
+* Bit 3: Set if the D&#8722; line has gone high.
 * Bit 4: Set if the ID line has gone low.
 * Bit 5: Set if the ID line has gone high.