When the last digit of the LeN is entered, the "packet-type" field appears, making the following softkeys available:
. . . . Q.II •. "" lUI . . lID P"·' •
.... ;'0". Ell ...
1 ••••V'''. . . II""UI"
The default packet type is Data. If ',,,lpJ:I was chosen in the GFI field, the packet-type field expands to two bytes for some packet types, as described below.
Data Packet Fields
The Packet-Type field for a data packet is like the control field for an I-frame. Entry of the peS), M, and peR) is just like the entry of N(S), P
IF,
and N(R) fields. When you select _ packet, the least significant bit (right-most) becomes zero, indicating a data type packet. Then you are prompted to fill three fields from right to left. peS) and peR) each require three bits; M requires one bit.peR) I M I peS) 0
If you selected ',,,lpJ:I in the GFI, the packet-type field consists of two bytes rather than one. peS) and peR) each take up seven bits:
(nherPacketTypes
RR, REJ, and RNR packet types have a peR) field. All other packet types do not have any such fields except Data.
Level 2 and 3 Assisted Mode 6 - 9
Entering a Level 2 "When" String -- An Example
The following example describes the procedure for entering a level 2 "when" string. The setup protocol must be either SDLC, HDLC, or X.25 to see the
'm*.I
softkey. If you don't see the indicated softkey, press MORE until you do. In the following example flags are shown as"I"·
1. Set protocol to SDLC in the Setup menu.
2. In the monitor or simulate menu, press
.,IeIQ.I.".'
and then ~ or ~. Let'sselect
EDII .
When OTE
then goto Block 2
3. Press
'm*.I.
The start flag and the address field (00) now appear:When OTE 100
then goto Block 2
4. Type the address in hexadecimal. Let's type "4A". The control field now appears in binary unless extended address is ON; and the softkeys prompt you to select the type of frame, which is determined by the least significant one or two bits (on the right).
When OTE 14AOOOOOOOO then goto Block 2
5. Let's select
'Di;M •.
The least significant bit (on the right) remains O. The cursor now moves to the left into the three-bit N(S) field. Enter an N(S) of 5.When OTE 14A00001010 then goto Block 2
6. The cursor now moves to the left into the one-bit P
IF
field. Let's enter a PIF
of 0.Note that even though the P
IF
bit is already 0, you must still enter°
to automatically move the cursor into the next field. Of course, you can always use the cursor keys.When OTE 14A00001010 then goto Block 2
6 -10 Level 2 and 3 Assisted Mode
7. The cursor now moves into the three-bit N(R) field. Let's enter an N(R) of 7.
When OlE 14A11101010 then goto Block 2
As soon as you make the entry the eight -bit control field collapses to its hex equivalent to save space:
When OlE 14AEA then goto Block 2
8. The cursor now moves into the I-field, prompting you to enter text.
Level 2 and 3 Assisted Mode 6 - 11
Entering a Level 3 "When" String -- An Example
The following example illustrates level 3 assisted entry for a "when" string. If you don't see the indicated softkey, press MORE until you do. The setup protocol must be either SDLC, HDLC, or X.25 to see the
.mw,
softkey. In the following example,"I"
indicates flags,"GG" indicates a good frame check sequence, "don't care" characters are shown as "x", and characters with no hex equivalent as "?".
1. Set the protocol to SDLC in the Setup menu.
2. In the monitor menu or simulate menu, press
IW"g.I'i'.1
and thenEDII .
When OTE
3. Press
Imw,.
The flag is automatically entered and the next two bytes, address and control, are shown as "don't care".When OTE Ix?
4. The first byte (level 2) is indicated by "x", which means "don't care". The cursor is positioned on the third byte, where level 3 entry begins. This byte is shown as unknown (?) because some of its bits are "don't cares".
At any point you can change the first two bytes by moving the cursor to the left and pressing
1'#)#*1 .
5. When the cursor is positioned on the third byte (?), three softkeys appear:
&II, IIBI,
and'IAU-'i..
PressEIDI;
the third byte now expands to eight binary bits, with the last four bits being "don't cares". The GFI consists of the first four bits on the left. The cursor now prompts you to enter the Q bit, which is the first bit on the left.When OTE Ixx0001xxxx
6. N ow enter the Q and D bits. Press 0 to enter a Q bit of O. The cursor now moves one bit to the right, prompting you to enter a D bit. Press the 1 softkey to enter aD bit of 1.
When OTE Ixx0101xxxx
6 -12 Level 2 and 3 Assisted Mode
7. The cursor now moves into the modulo 8 or 128 field, which consists of the third and fourth bits from the left. Press
',rm
l :!, which is 01.When OlE Ixx0101xxxx
8. The cursor now moves into the last four bits, which is the LCGN field. You can enter a maximum of 15 decimal; if you type a number higher than 15, the entry defaults to 15. Type 09 (note that you must enter leading O's to have the cursor move
automatically). The third byte collapses to its hex equivalent, and the cursor moves to the fourth byte.
When OlE Ixx01011001 becomes When OlE Ixx5900000000
9. The fourth byte is the LCN. You can enter a maximum of 255 decimal; if you type a number higher than 255, the entry defaults to 255. Type 045 or select hex entry and enter 2D (note that you must enter leading O's for the cursor to move automatically).
The fourth byte collapses to its hex equivalent, and the cursor moves to the fifth byte.
When OlE Ixx5900101101 becomes When OlE Ixx592000000000
10. The fifth byte is the packet-type identifier. The cursor moves to the least significant bit (most right). A least significant bit of 0 indicates a "data" packet. Let's select a data packet type by pressing . . . The least significant bit remains O.
11. The cursor now moves to the left into the three-bit peS) field. Type 7.
When OlE Ixx592000001110
12.
..•
The cursor moves to the M bit, which is the fUth bit from the right. Press"",.
When OlE Ixx5920000x1110
13. The cursor moves to the three-bit peR) field, which is the last three bits from the left.
Type 5. The futh byte collapses to "?" because there is no hex equivalent.
When OlE Ixx5920101x1110 becomes When OlE Ixx5920?
14. The cursor moves into the text field, allowing you to type any text you wish. Type
"THIS IS TEXT".
When OlE Ixx5920?lHIS IS lEXl
Level 2 and 3 Assisted Mode 6 - 13
15. Press
'ml',hni,
and thenId.i.i.li .. ' .
Note
When OTE Ixx5920?THIS IS TEXT GGI then goto Block 2
The trigger counter at the bottom of the display should indicate "42 triggers left".
Therefore, the entire string used up 63 - 42, or 21 triggers.
You may not have needed to trigger on the complete string. You can trigger on any character or characters in the string. For example, if you wish to trigger only on packets which have an LeN of2D, you can enter the following:
When OTE Ixxxx20
This tells the analyzer to look for a 2D in the fIfth byte after any start flag.
6 - 14 Level 2 and 3 Assisted Mode