*_Functional Specification of SAB8253X ASLX Driver for Linux_* The SAB8253X serial interface chip is very flexible.  It supports mostof the standard asynchronous serial transmission modes as well assynchronous Bit Oriented Protocols (BOPs) and character orientedprotocols.  The Linux ASLX Driver system provides an extremely flexibleLinux interface to the SAB8253X serial interface chips that are used onthe Aurora <http://www.auroratech.com/> XX20 adapter cards andMultichannel server units whether they are inserted directly into a hostbus or whether they are connected via a PCI extension system such as theAurora XP7.   Supported Hardware The Linux ASLX Driver supports Aurora SAB8253X communications adaptercards and systems for PCI bus systems.  Possible adapter cardconfigurations are identified as MN20 where M is 1, 2, 4, 8 and N is 0or 5.  M is the number of ports.  N = 0 means that the adapter card doesnot support synchronous modes.  N = 5 means the adapter card modes areunrestricted.  The multichannel server system consists of an hostadapter card that attaches to an expansion box via the G-Link connectioncable.  The expansion box can host 2000, 2500 and 3500 type ExpansionBoards (EBs).  The 2000 EB provides 15 asynchronous-only RS-232 portsand 1 unrestricted RS-232 port.  The 2500 EB provides 16 unrestrictedRS-232 ports.  The 3500 EB provides 16 unrestricted serial ports, whosephysical signaling is under software control.  The XP7 is a PCIexpansion chassis.  The ASLX correctly identifies the Aurora adapter card or Multichannelserver and EBs, determines capabilities and provides a softwareinterface to configurable capabilities (e.g., a choice of RS-232 [= thedefault], RS 422/423, RS 449, EIA 530, V.35, X.21, RS-485 and none[=off] signaling for 3500 EBs).  The use of an XP7 should be transparentto the driver.  The ASLX driver will automatically correct incorrectlyprogrammed adapter card or Multichannel server serial EEPROMs. Moreover, in addition to the primary serial communications interface,the ASLX driver provides a ^觤aintenance^