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PDA Robotics
from the time its LED finishes transmitting to the time its receiver
diode is capable of receiving, the remote station must wait 1 ms from
receiving the last bit of a frame before beginning to transmit a new
frame. The remote station performs this wait to honor the local trans-
ceiver’s turnaround time.
To honor the turnaround time of the remote transceiver, the IrLAP pro-
tocol might sometimes specify to delay transmission of a packet. To do
so, the IrLAP protocol specifies the amount of time before a packet
should be transmitted. The IrDA miniport driver must not transmit the
packet before waiting the requested amount of time, although the driv-
er can wait longer if necessary. The IrLAP protocol specifies transmis-
sion delay time of a packet in the media-specific member of the pack-
et’s associated out-of-band (OOB) data block.
IrLAP defines the format of the frames sent and received on the IR
media. Each IrLAP frame consists of the following elements:

• One or more beginning of frame (BOF) flags that mark the begin-
ning of the frame. The size of the BOF member varies in length,
depending on the speed.

• An address (A) member that identifies the secondary connection
address. The address member is 8 b. The address member speci-
fies the address of a device that belongs to a particular IrDA mini-
port driver. This IrDA miniport driver transmits or receives the
frame that contains this address through this device.

• A control (C) member that specifies the function of the particular
frame. The control member is 8 b.

• An optional information (I) member that contains the informa-
tion data. The information member is an integral number of
octets.

• A frame check sequence (FCS) member that allows the receiving
station to check the transmission accuracy of the frame. The FCS
member is either 16 or 32 b, depending on the speed.
• An end of frame (EOF) flag that signals the end of the frame. The
size of the EOF member varies, depending on the speed.

The following example of an IrLAP frame shows the order of the ele-
ments that were described in the preceding section.

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