Difference between revisions of "83Plus:Ports:93"
(Port 93: maximum packet size for reading) |
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[[Category:83Plus:Ports:By Address|93 - USB Read Packet Size]] [[Category:83Plus:Ports:By Name|USB Read Packet Size]] | [[Category:83Plus:Ports:By Address|93 - USB Read Packet Size]] [[Category:83Plus:Ports:By Name|USB Read Packet Size]] | ||
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== Synopsis == | == Synopsis == | ||
'''Port Number:''' 93h | '''Port Number:''' 93h | ||
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This port controls the maximum packet size allowed for data read from a USB pipe. | This port controls the maximum packet size allowed for data read from a USB pipe. | ||
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=== Read Values === | === Read Values === | ||
Latest revision as of 20:25, 27 October 2011
| 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 03. On the TI-83 Plus Silver Edition, this port has no effect. |
Synopsis
Port Number: 93h
Function: USB Read Packet Size
This port controls the maximum packet size allowed for data read from a USB pipe.
Read Values
- Unknown
Write Values
- Bits 0-7: Maximum packet size for the current pipe, divided by 8.
Comments
This port tells the USB controller the maximum allowed packet size for data read from the current pipe. (The "current" pipe is determined by 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.
In host mode, it's important to know the maximum packet size for incoming endpoints, so that the USB controller can schedule transactions properly. I'm not sure what effect this port has in peripheral mode. In any case, it seems wise to configure this port, along with port 9A (bEndpointAddress / bmAttributes), and possibly port 9B (bInterval), before requesting any data from a pipe.
