NOTE: This Technical Note has been
retired. Please see the Technical Notes
page for current documentation.|
Bad Character Bits Are Not Passed to an Application
Because the IOP does not return the bits of a character which is received with
a parity error, the A/UX driver always returns NUL to an application.
Applications which use
Break Always Returns a NUL to an Application
Because the IOP always returns a NUL character when a break occurs, the A/UX
driver passes it along to an application. There is no way for the driver to
determine that the NUL is superfluous. Other break processing is unaffected.
Programs which use
Multiple Errors in a "Chunk" of Characters Are Not Reported
The IOP only reports parity and framing errors on the first such occurrence in
its internal buffer. The A/UX driver always reads characters in "chunks" from
the IOP; therefore, only the first error is reported and subsequent errors go
unnoticed. For example, assume an application sets
This situation causes two problems:
Since the timing of the A/UX driver's "chunk reads" and the arrival of data can vary, there is no way to predict or prevent the occurrence of this problem.
The Current "DMA Hang" IOP Code Patch is Incomplete
The existing IOP code has been patched, both under the Macintosh OS and A/UX, to code around a bug in its DMA logic. Should any errant characters be received during servicing of a DMA operation, the IOP silently discards them, never reporting any error. This can cause unreported dropping of characters. Since this situation is timing-dependent, there is no way to predict or prevent the occurrence of this problem.
IIfx Serial Switch cdev
The IIfx Serial Switch cdev does not, itself, work under A/UX. If users need to enable "Compatibility" mode, they should do so first under the Macintosh OS. A/UX, upon booting, honors the switch setting in parameter RAM. Refer to M.HW.MacIIfx for more details on the IIfx Serial Switch cdev.
A/UX System Administrator's Reference
Contact ADC | ADC Site Map | ADC Advanced Search
|For information about Apple Products, please visit Apple.com.|
Contact Apple | Privacy Notice
Copyright © 2002 Apple Computer, Inc. All rights reserved.