This is particularly important for Type 2 devices are programming an UART based on the control parameters sent from the other side. This parameter allows a Type 2 device to report back error conditions resulting from the line settings issued to it by a Type 1 device. If not sent, the defaults are 0x11/0x13 for XON/XOFF, and 0x05/0x06 for ENQ/ACK. These parameters allow different characters to represent XON/XOFF and ENQ/ACK when those types of flow control are used.
The Flow Control parameter supports this capability as well.ĩ.3.4XON/XOFF and ENQ/ACK Flow Control Characters In addition, some operating systems allow multiple flow control mechanisms to be set simultaneously. Some operating systems allow flow control to be set independently for incoming data and outgoing data. If not sent, the default is no flow control. The Flow control parameter represents the flow control type (or types) set by an application on a device. If the parameter is not sent, the default of 8 bit, no parity, 1 stop bit is assumed. The Data Format parameter represents the value set by an application on a device. If this parameter is not sent the data rate is undefined. The Data rate parameter represents the value set by an application on a device. The table below defines the parameters used by 3-Wire emulation to deliver the port communication settings and port line status:Įach parameter is described below in detail. for certain Type 2 devices to deliver port line status (overrun, parity and framing errors) back to Type 1 devices.to exchange port communication settings (data rate, data format, and flow control information) when emulating a serial port.
In 3-Wire, the control channel is used for three purposes: If hardware handshaking is required, the 9-Wire or Centronics service types are necessary. This illustrates a fundamental distinction between 3-Wire raw and 3-Wire in the 3-Wire case, IrCOMM must monitor incoming packets for control channel information.ĭespite the presence of the control channel, 3-Wire cannot emulate hardware handshaking, since the non-data circuits are not emulated. The solution is to send the service type control parameter through the control channel, discussed in the next section. This is because 3-Wire uses Tiny TP flow control, a method which does not flow control off the entire physical link.Īt connection, the 3-Wire service type may not be distinguished reliably by its LsapSel alone unlike 3-Wire raw it may share use of the IAS LsapSel entry with the other cooked types. Unlike 3-Wire raw, 3-Wire connections can coexist with other non-exclusive IrLMP connections. It should also have the printer bit set if this is a printing service. The Discovery frame must have the IrCOMM hint bit set.
Parameters attribute - The Parameters attribute must have the service type parameter with at least the 3- Wire bit set in it.IrDA:TinyTP:LsapSel attribute indicating the LSAP selector at which the service is located.If this is all a port needs to function, then 3-Wire may be fine.Īn entity advertising 3-Wire capability has an IAS entry with the following characteristics: 3-Wire can emulate serial or parallel because no information about the non-data circuits of either type is carried - just the bytes normally flowing on the data circuits, and in the serial case some setup and status information. 3-Wire may be used to emulate either serial or parallel ports in cases where more than one connection may be desirable.