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|d|i|g|i|t|a|l| INTEROFFICE MEMORANDUM
---------------
TO: DECnet Users DATE: 22-Feb-80
FROM: NCSS
EXT: HOTLINE (5911)
LOC/MAIL STOP: MR1-2/H22
SUBJ: Use of DATASCOPE with DECnet
The Spectron Datascope is a monitoring device which can display
all the data transmitted and received over a physical line. It is
hooked into the line between the modem and the physical line
driver. It can be used for diagnosing communications problems
over a wide range of protocols, devices, and speeds.
The Datascope is about the size of a small oscilloscope. The
characters on the line are displayed on a small screen. There are
lots of controls for setting the byte size of the characters, the
way in which the bits are to be interpreted, and how the display
is to be formatted.
Some models of the Datascope can be programmed to do things like
search for certain character patterns and stop the display and so
on. Some can be used with a tape unit which can record the line
activity for analysis later.
The Datascope is the best tool we know of for determining exactly
what is happening on a communications line. Unfortunately, it is
very expensive, costing many thousands of dollars. For this
reason, individual offices almost never have a Datascope of their
own. Nonetheless, if you will be doing a network installation or
will be otherwise involved in potentially difficult network
problems, it is a good idea just to inquire into the availability
of a Datascope in case the need for one should arise. Some
districts or regions own one Datascope which can be loaned out to
its local offices. If you are lucky and are involved with a rich
customer, the site may have one of its own.
If there is no way you can get your hands onto a Datascope, look
into using DNSR. This program is documented elsewhere on the
DECnet SWSkit. A breakout box, which costs only a few dollars,
may also be helpful. This can at least tell you what is happening
with the EIA modem signals and whether data is being sent or
received.
Page 2
The Spectron people offer a course on the use of the Datascope. A
quicker way to learn its use is to simply find someone who knows
how to use it and to ask him or her to show you how it works. The
controls are simple and an hour or two of hands-on time should be
plenty.
The remainder of this memo describes how to use the Datascope for
diagnosing DECnet problems. The Datascope may also be used for
BISYNC (2780/3780/HASP) communications. See Large Buffer volume
463, page 25, for information on BISYNC Datascope settings.
1.0 HOOKING UP THE DATASCOPE
The Datascope is hooked into the line between the line driver (DUP
or DMC) and the modem. First use the NCP command subset of OPR to
set the state of the line to OFF. Then plug the EIA connector
coming out of the DN20 for that line into the back of the
Datascope in the position marked "Bus Mach/RCU". Then patch a
plug between the "modem" connector on the Datascope and the modem.
Then power on the Datascope and turn the line on again. Note that
the datascope need not be on for the link to work.
If your synchronous lines go through a Spectron or similar patch
panel, you can hook the Datascope into the patch panel. Insert a
patch between the monitoring plug for the modem on the patch panel
and the "Bus Mach/RCU" plug on the Datascope. In other words, the
Datascope is acting as the monitor rather than the regular
monitoring plug on the side of the patch panel. This saves you
the trouble of having to turn the line on and off from OPR and
connect and disconnect the cables. To make this patch, you will
need a cable with a patch panel connector on one end and a male
EIA connector on the other end.
2.0 LIGHTS
The row of lights across the display corresponds to the EIA-CCITT
modem-terminal interface. For example, if light 8 is on, it
indicates that Carrier Detect, pin 8, is high. This display is
the same as the display in a breakout box. A listing of the pin
numbers is included later on in this memo.
3.0 DATASCOPE SWITCH SETTINGS
Settings suitable for looking at DECnet transmission are indicated
by *.
Page 3
Switches Settings
2 char/normal *2 char - sync on one occurrence of 2
char pattern
Normal - sync on double occurrence of 1
char pattern (leftmost char on
thumbwheels)
Internal/modem Internal clocking
*Modem clocking (null modems must have
clocking)
Manual *On
1-8/8-1 1-8 reverse order of refresh memory, 8
arrives first
*8-1 normal order, bit 1 arrives first
Send Up - invert polarity of send signal
(converts ones to zeros and zeros to
ones)
*Down - normal polarity
Rcv Up - invert polarity of receive signal
*Down - normal polarity
Both Up - invert polarity of send and receive
signal
*Down - normal polarity
Dials
Send/Rcv
SEND *Display send-data only (pin 2)
RCV *Display receive-data only (pin 3)
HDX-4 Display both send and receive in time
sequence (1 line/timeframe).
Simultaneous 2 way transmission is
garbled. Excellent for 4-wire
half-duplex.
HDX-2 Display send-data when RTS is high (pin
4)
Display receive-data when RTS low (CD
high pin 8)
FDX *Display send/receive on alternate lines
(2 lines/timeframe). Ideal for
full-duplex.
Page 4
Framing (the bit count includes the parity bit)
ASYNC Selects 5 to 8 bits per character for
start/stop character framing
SYNC *Selects 5 to 8 bits for synchronous
character framing. Use Sync-8 for
DECnet (8 bits).
SDLC Interprets incoming data using SDLC
protocol
OFF Disables automatic sync
Code
HX *Hexadecimal. Use as a double-check on
ASCII characters or for extracting
binary fields from messages. See
the HEX-ASCII-binary conversion
chart later in this memo.
A *ASCII
B EBCDIC
C,D Optional codes
Marker
OFF *All characters white on black
ODD Characters with odd parity black on
white
EVEN Characters with even parity black on
white
CD *Characters arriving while Carrier Detect
(pin 8) high black on white. Use
this if you suspect carrier is
dropping occasionally.
FDX When FDX set above
Received data black on white when CD
high (pin 8)
Send data black on white when RTS high
(pin 4)
Otherwise, same as RTS
RTS Characters arriving while Request to
Send (pin 4) high black on white
EXT Characters arriving while external
signal present black on white
Suppress
OFF *Shows all activity on line very fast.
Time relationships can be seen.
MARK *Delete all idle characters except 4
before and 4 after non-idle period
(hopefully a message). Only
suppresses screen display, all info
Page 5
goes to buffer and/or tape.
Thumb-wheels
Speed *Used only if clocking is internal. Set
to N to insure default to modem
clocking.
Framing pattern *Set to 9696 (ASCII SYN SYN)
Sync reset *Set to FF drop sync 4 characters after
trailing pad encountered. Watch out
for trailing pads embedded in
messages; you can lose end of
message.
Rocker switch
Display Run - clear display and reconnect to
line
Stop - freezes screen and allows
scrolling. Leave on run until you
want to examine the info on the
screen. Then quickly push Stop.
The last 2000 characters are stored
in a buffer, but fill characters
will quickly fill the buffer even if
the display is not moving. You have
to move quickly not to lose the
info. When the button is pushed,
the screen will display the last few
characters in the buffer. You must
use the scrolling buttons to see
previous characters.
Scroll Scroll through buffer back from last
data received. Can be moved
forwards or backwards.
4.0 HEX-ASCII DATA CONVERSION
The following chart can be used to convert 8-bit ASCII to HEX. It
can also be used to obtain the binary for each HEX digit. To
convert from HEX to ASCII, choose the first HEX digit from the top
and the second HEX digit from the left, and then look where the
row and column meet. To convert from ASCII to HEX, choose the
second HEX digit from the row in which the character appears and
the first HEX digit from the column. The reason there are two
choices for the first HEX digit is because parity may be odd,
even, or non-existent. For no parity, choose B8=0. For even or
odd parity, choose either B8=0 or B8=1, whichever one will give
you the right number of 1 bits.
Page 6
For example,
ASCII "L" = 4C (no parity)
= CC (even parity)
= 4C (odd parity)
|------------------------------------------------|
| B7----------->|0 |0 |0 |0 |1 |1 |1 |1 |
| B6-------->| 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 |
| B5----->| 0| 1| 0| 1| 0| 1| 0| 1|
|---------------\ | | | | | | | |
| 1st HEX B8=0 \ | | | | | | | |
| Digit ----\ ---|---|---|---|---|---|---|---|
| B8=1 \ 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|--------------\ ---|---|---|---|---|---|---|---|
| 2nd HEX Digit \ 8 | 9 | A | B | C | D | E | F |
|----------- ||---|---|---|---|---|---|---|---|
|B4|B3|B2|B1| || | | | | | | | |
|--|--|--|--|---||===|===|===|===|===|===|===|===|
| 0 0 0 0| 0 ||NU |DL | | 0 | @ | P | ` | p |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 0 0 1| 1 ||SH |D1 | ! | 1 | A | Q | a | q |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 0 1 0| 2 ||SX |D2 | " | 2 | B | R | b | r |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 0 1 1| 3 ||EX |D3 | # | 3 | C | S | c | s |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 1 0 0| 4 ||ET |D4 | $ | 4 | D | T | d | t |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 1 0 1| 5 ||EQ |NK | % | 5 | E | U | e | u |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 1 1 0| 6 ||AK |SY | & | 6 | F | V | f | v |
|-----------|---||---|---|---|---|---|---|---|---|
| 0 1 1 1| 7 ||BL |EB | ' | 7 | G | W | g | w |
|-----------|---||---|---|---|---|---|---|---|---|
| 1 0 0 0| 8 ||BS |CN | ( | 8 | H | X | h | x |
|-----------|---||---|---|---|---|---|---|---|---|
! 1 0 0 1| 9 ||HT |EM | ) | 9 | I | Y | i | y |
|-----------|---||---|---|---|---|---|---|---|---|
| 1 0 1 0| A ||LF |SB | * | : | J | Z | j | z |
|-----------|---||---|---|---|---|---|---|---|---|
| 1 0 1 1| B ||VT |EC | + | ; | K | [ | k | { |
|-----------|---||---|---|---|---|---|---|---|---|
! 1 1 0 0| C ||FF |FS | , | < | L | \ | l | | |
|-----------|---||---|---|---|---|---|---|---|---|
| 1 1 0 1| D ||CR |GS | - | = | M | ] | m | } |
|-----------|---||---|---|---|---|---|---|---|---|
| 1 1 1 0| E ||SO |RS | . | > | N | ^ | n | ~ |
|-----------|---||---|---|---|---|---|---|---|---|
| 1 1 1 1| F ||SI |US | / | ? | O | _ | o |DT |
|------------------------------------------------|
Page 7
5.0 FINDING NSP MESSAGES ON THE DATASCOPE
The Datascope shows DDCMP messages as they are passed between two
nodes. Some of these messages are control messages and are sent
only to verify the error-free transmission of data. Only some of
the messages will contain NSP messages.
A DDCMP message which contains an NSP message will look something
like the templates shown below. The first example shows the HEX
output, and the second shows the ASCII output, in which ? is used
to mean any arbitrary character.
FF FF FF FF 96 96 96 96 96 81 xx xx xx nn 01 xx xx
{NSP data} xx xx FF FF FF FF
DT DT DT DT SY SY SY SY SY SH ? ? ? ? SH ? ?
{NSP data} ? ? DT DT DT DT
The number of sync characters (96 or SY) may not be exactly the
same as shown here. In addition, the delete characters (FF or DT)
may be omitted between messages if the traffic is heavy. The key
number to look for is 81 (control character SH in ASCII) after a
large number of sync characters. This is the DDCMP code which
says that this is a data message. The 8th character after the 81
is the first character of the NSP data. The NSP data continues
all the way to the end of the message except for the last two
characters, which are the DDCMP block check.
The character marked as nn is the DDCMP number of this message.
Send and receive messages are numbered separately but, within that
condition, the number should increase by one for each new message.
If you find a message with the same number as the last one, the
message had to be repeated because of an error in transmission.
Throw out the old message and use the new one instead.
For the interpretation of the NSP data, see the NSP specification.
Page 8
6.0 EIA PIN DEFINITIONS
+----------------------------------------------------------------+
| Pin| Name |To To | Function | Circuit |
| | |DTE DCE| |(CCITT) (EIA) |
|----+------+-------+----------------------------+-------+-------|
| 1 | FG | | Frame Ground | 101 | (AA) |
| 2 | TD | > | Transmitted Data | 103 | (BA) |
| 3 | RD | < | Received Data | 104 | (BB) |
| 4 | RTS | > | Request To Send | 105 | (CA) |
| 5 | CTS | < | Clear To Send | 106 | (CB) |
| 6 | DSR | < | Data Set Ready | 107 | (CC) |
| 7 | SG | | Signal Ground | 102 | (AB) |
| 8 | DCD | < | Data Carrier Detect | 109 | (CF) |
| 9 | | < | Positive DC Test Voltage | | |
| 10 | | < | Negative DC Test Voltage | | |
| 11 | | | Unassigned | | |
| 12 | SDCD | < | Sec. Data Carrier Detect | 122 | (SCF) |
| 13 | SCTS | < | Sec. Clear To Send | 121 | (SCB) |
| 14 | STD | > | Sec. Transmitted Data | 118 | (SBA) |
| 15 | TC | < | Transmitter Clock | 114 | (DB) |
| 16 | SRD | < | Sec. Received Data | 119 | (SBB) |
| 17 | RC | < | Receiver Clock | 115 | (DD) |
| 18 | | > | Receiver Dibit Clock | | |
| 19 | SRTS | > | Sec. Request To Send | 120 | (SCA) |
| 20 | DTR | > | Data Terminal Ready | 108.2| (CD) |
| 21 | SQ | < | Signal Quality detect | 110 | (CG) |
| 22 | RI | < | Ring Indicator | 125 | (CE) |
| 23 | | > | Data Rate Select |111/112|(CH/CI)|
| 24 | (TC) | > | External Transmitter Clock | 113 | (DA) |
| 25 | | > | Busy | | |
+----------------------------------------------------------------+
[End of DATASCOPE.MEM]