User manual

36DCA Intertel DCA Intertel
DCA Intertel 37 DCA Intertel
2.3.1.5.3 IAS entry and hint bits
An entity advertising 3-Wire raw must set up the IAS entry in one of two
forms:
• Classname IrDA:IrCOMM with two attributes, called IrDA:IrLMP:LsapSel,
and Parameters. The Parameters attribute has at least the service type
parameter with at least the 3-Wire raw bit set in it.
Optionally IrDA:IrLMP:InstanceName can be used to distinguish between
two instances of this service. The Discovery frame must have the IrCOMM
hint bit set. It should also have the printer bit set if this is a printing service.
• An alternate entry provided for backwards compatibility with some existing
devices has Classname IrLPT with just one attribute, called IrDA: IrLMP
:LsapSel. The printer hint bit must be set in the Discovery frame. This IAS
object is only used for printing services.
2.3.1.5.4 Basic link operation
3-Wire raw connections must be exclusive - that is, all other non-IAS
connections must terminate before the raw connection is made, and all
others must wait until the raw connection is broken before they can connect.
This is because 3-Wire raw uses IrLAP ow control, which ow controls off
the entire physical link - multiple connections under this scenario could result
in deadlock. At connection, the 3-Wire raw service type can be distinguished
reliably by its LSAP-SEL alone, since unlike the cooked types (where multiple
service types can be referenced by IrDA:TinyTP:LsapSel) only 3-Wire
raw can use the LSAP-SEL specied by IrDA:IrLMP:LsapSel.
Once connected there is no control channel and no control parameters of
any kind to look for - the only data that comes over 3-Wire raw is the user
data that would ow over TD and RD on a serial port or the 8 data lines of a
Centronics port. This means 3-Wire raw cannot be used to emulate any kind
of hardware handshaking or error reporting.