| -- Test Center Showcase -- 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. |
