Trailing-Edge
-
PDP-10 Archives
-
BB-L289B-RK
-
brkout.mem
There is 1 other file named brkout.mem in the archive. Click here to see a list.
+---------------+
! d i g i t a l ! I N T E R O F F I C E M E M O R A N D U M
+---------------+
Date: 20-January-82
From: TSG/NCSS
Loc: MR1-2/H22
Ext: HOTLINE 5911
Subj: Use of a Breakout Box
The breakout box is a simple, cheap diagnostic tool which can be
used to monitor modem signals. This memo gives you some clues
regarding what to look for when using the breakout box.
If you are lucky and have a Datascope at your disposal, the top row
of lights on the Datascope may be used in lieu of a breakout box.
In either case, a quick check of the line using a breakout box may
be helpful if you suspect that the modems or the lines themselves
may be at fault.
1.0 INSTALLING THE BREAKOUT BOX
The breakout box is hooked into the line between the line driver and
the modem. Find a place in the line anywhere between the line
driver and the modem where a connection is made with a 25-pin EIA
connector. Break this connection and then reconnect the line with
the breakout box in the middle, whichever way the plugs will fit.
Be sure all the mini-switches on the box are set to normal, not
open.
2.0 TROUBLE SHOOTING
To determine if the character is being received and transmitted by
the line driver(interface), watch the TD and RD lights on the break
out box while characters are being typed on the terminal. If the TD
and RD lights both blink, the character is making it through the
common carrier system to the CPU and being sent back to the
terminal. If the TD light blinks and the RD light does not, the
character is making it to the CPU but is not being sent back. This
could mean a bad interface or malfunctioning software. If the TD
light does not blink, the character is not making it through the
common carrier system. Install the breakout box at the other end of
the line between the terminal and the modem. Now look at the TD and
RD lights on the break out box. If the TD light blinks, the
character is being sent by the terminal but is not making it through
Page 2
TROUBLE SHOOTING
the common carrier system. This means malfunctioning modems or
common carrier. If the TD light does not blink, the terminal is not
sending the character and you have a bad terminal.
3.0 EIA PIN DEFINITIONS
For your convenience, here is a list of all 25 EIA pins.
+----------------------------------------------------------------+
| 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 | | |
+----------------------------------------------------------------+