Thepenguin77 at 04:23, 28 October 2011

2011-10-28T04:23:27Z

FloppusMaximus: Port 90: maximum packet size for writing (?)

2010-11-15T03:57:19Z

Port 90: maximum packet size for writing (?)

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[[Category:83Plus:Ports:By Address|90 - USB Write Packet Size]] [[Category:83Plus:Ports:By Name|USB Write Packet Size]]
== Synopsis ==
'''Port Number:''' 90h

'''Function:''' USB Write Packet Size

This port controls the maximum packet size allowed for data packets written to a USB pipe.

{{84P-Only Port|10}}

=== Read Values ===
* Unknown

=== Write Values ===
* Bits 0-7: Maximum packet size for the current pipe, divided by 8.

== Comments ==
This port appears to be the analogue of [[83Plus:Ports:93|port 93]]. As such, it tells the USB controller the maximum allowed packet size for data written to the current pipe. (The "current" pipe is determined by [[83Plus:Ports:8E|port 8E]].)

The value written to this port is the maximum packet size, or the wMaxPacketSize field in the endpoint descriptor, ''divided by 8''. For an endpoint with a wMaxPacketSize that isn't a multiple of 8, you should presumably round up, but take care never to write more bytes than the actual wMaxPacketSize.

I'm not sure what effect this port actually has, in either host or peripheral mode. (Would the USB controller automatically split up a large transfer into multiple packets?) In any case, it seems wise to configure this port, along with [[83Plus:Ports:98|port 98]] (bEndpointAddress / bmAttributes), and possibly [[83Plus:Ports:99|port 99]] (bInterval), before writing any data to the pipe.

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 [[Category:83Plus:Ports:By Address|90 - USB Write Packet Size]] [[Category:83Plus:Ports:By Name|USB Write Packet Size]]
 == Synopsis ==
 '''Port Number:''' 90h
@@ Line 6: / Line 7: @@
 This port controls the maximum packet size allowed for data packets written to a USB pipe.
 === Read Values ===

83Plus:Ports:90 - Revision history

Thepenguin77 at 04:23, 28 October 2011

FloppusMaximus: Port 90: maximum packet size for writing (?)