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D) ** "TEST FRAME" SOURCE CODE FOR BIT-ERROR-RATE TEST:

The source codes to effect such efficient Test Frame implementation is 
listed as follows:

When the station is playing the secondary role in 
Normal Response Mode (NRM) and an incoming frame 
is received, one normally checks the following:

a) the CRC is correct
b) the C/R bit is set
c) the connection address is intended for this 
station

If the incoming frame passes all these, one then 
examines the Control field and takes the 
appropriate action accordingly. This can 
be implemented as a chain of "if (...) {...}", 
"else if (...) {...}", ..., "else {...}". 

To implement the test frame option, one needs 
to add the following code to that chain:
..............................................

else if (frame_buffer[1] == 0xF3)
/* test frame + P bit received */
{
frame_buffer[0] &= 0xFE;
/* clear the C/R bit */

transmit (frame_buffer, incoming_size);
/* bounce it back with C/R bit cleared */
}
..............................................

The procedure "transmit(...)" calculates the CRC 
and sends the frame out. The very first bit in the 
frame buffer (i.e., the C/R bit) is changed, thus 
the outgoing CRC will be totally different 
from that of the incoming frame. 
----------------------------------------------

The Test Frame is already an optional feature in both IrLAP
1.0 and IrLAP 1.1. For example the IrLAP 1.1 State Chart for 
Secondary Role State Machine, NRM(S) in Section 6.12.4.1, 
under: 
Current State = RECV 
Event = Recv u:test:cmd:P

There are two alternative Actions. Alternative 1 is:
Wait-Minimum-Turnaround-Delay
send u:test:rsp:F
Start-WD-timer

And alternative 2 is:
Wait-Minimum-Turnaround-Delay
Send s:rr:rsp:Vr:F
Start-WD-timer

After either alternative Actions are taken, 
Next State = RECV

We suggest to use alternative 1 instead of alternative 2. 
That is, respond with u:test:rsp:F, and not 
s:rr:rsp:Vr:F.