Report Io. 2277 Bolt Beranek and Newman Inc.
EIA CONNECTOR MAY BE EITHER PLACE-
I
PATCH PANEL ON LIU
½OMPONENT SIDE OF BOARD UP
FIG. A-1 LIU PIN DIAGRAM
32 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
TABLE A-1
STANDARD LIU PATCH PANEL CONFIGURATIONS
LiU pin for connection to:
EIA
PIN TERMINAL 103
1 E1 E1
2 E3 E2
3 E2 E3
4 E5 E4
5 E4 E5
6 El9 E6
7 E7 E7
8 E20 E8
10 ....
11' Eli Eli
12 El2 El2
13 El3 El3
14 El6 El4
15 El7 El5
16 Ei4 El6
17 El5 El7
18 ....
19 E6 El9
20 E8 E20
21 ....
22 ....
23 ....
24 E25 E24
25 E24 E25
When a card is wired for a particular configuration, it is
customary to specify that configuration (e.g. "M103" or "T")
on the plastic block on the LIU card.
*Not all LIU cards have this wire. It is not necessary for
operating 103 modems, or any terminals we know of.
33 6/73
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APPENDIX B
TERMINALS WHICH HAVE BEEN
CONNECTED TO A TIP
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HAZELTINE 2000
Descri pti on:
The Hazeltine 2000 is a video display terminal capable of data
rates from 110 to 9600 baud, full- or half-duplex. Its screen
can hold up to 27 lines of up to 74 characters each. Hard copy
and tape cassettes are available options. This terminal is
designed to operate over 103- or 202-type modems, or to be
connected directly.
Connection to the TIP:
This terminal comes with an EIA RS-232B interface which may be
connected directly to a "T" LIU card (see Appendix A). The
DATA TERMINAL READY lead is controlled by the POWER switch, and
is not affected by any keyboard buttons.
The parity switch should be set to 1; the others may be set as
desired.
Operati on:
When the terminal comes on, make sure the rate is set to i10,
150, or 300, and type E. In this case, SHIFT and E cause the
character U to be produced, so just type E. When HELLO is
receive6, it is possible to set up other device rates as
described in the TIP User's Guide, then the terminal can be
changed to the other speed.
37 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
HAZELTINE 2000 (Page Two)
The Hazeltine 2000 does not respond eli to cycling power ON and
OFF*; therefore, try to get HELLO before typing many other
characters.
*According to the Hazeltine Service Representative, there is a
design flaw in the power supply, such that about one time in
ten power does not come up properly. If this happens, turn
power off, wait 15 seconds and try again.
38 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
Model:
IBM 2741
(presently - inquire for Bthers)
2741 Correspondence models*
001 007 010 012
015 019 029 043
2741 PTTC models*
938 939 942 943
947 948 961 962
963 996 997 998
For operation with the TIP, it is necessary to have the 2741
equipped with the following options:
IBM Sales Number
Transmit Interrupt 7900
Interrupt 4708
Data Set 9114
Dial-up 3255
If any difficulty occurs in ordering these options, contact BBN.
Descri pti on:
The IBM 2741 is a hard-copy terminal which operates at 134.5 baud,
half-duplex. Its keyboard and printer are very similar to a
Seiectric typewriter.
Connection to the TIP:
With the 2741 equipped as required, it is only necessary to plug
its EIA compatible plug into an LIU which has been configured
for terminals (see Appendix A).
*The model number is hidden on the typeball.
39 9/72
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,Report No. 2277 Bolt Beranek and Newman Inc,
IBM 274i (Page Two)
Operati on:
Turning power ON connects the terminal and starts "hunt" mode.
See the TIP User's Guide, Section I for the appropriate character
for describing this terminal to the TIP.
See the TIP User's Guide, Section V for a description of the
code conversion for sending the full ASCii character set from
a 2741.
4O 9/72
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Report No. 2277
Bolt Beranek and Newman Inc.
INFOTON VISTA
Version: VISTA 1H
Des cri pti on:
The Infoton Vista is a video display terminal capable of data
rates from 110 to 4800 baud, full- or half-duplex. Its screen
can hold up to 20 lines of 80 characters each. It is presently
able to operate over 103 modems, and perhaps will operate over
202 modems in the future. Its standard interface allows EiA
or Teletype compatible current loop connection.
Connection to the TIP'
This terminal comes with the Multipurpose Asynchronous Serial
Interface which provides an EIA connector which may be connected
directly to a "T" LIU card (see Appendix A).
The controls can be set as desired.
Operation:
When the terminal comes ON, make sure the rate is set to 110,
150, or 300 and type E. When HELLO is received, it is possible
to set up other device rates as described in the TIP User's Guide.
The terminal can then be switched to that rate.
Turning power off disconnects the terminal.
41 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
TELETYPE MODEL 37
Vers i on: KSR
For proper connection to the TIP, the "OUT OF SERVICE" feature
must be available:
Des cri pti on:
The 37 KSR TTY set is a heavy duty hard copy terminal capable
of operating at 100 or 150 words per minute (110 or 150 baud).
It is capable of printing upper and lower case, and may be used
over a 103 modem. It has many variable user features.
Connection to the TIP:
To connect a 37 TTY to the TIP, it is necessary to strap the
following options. These jumpers are found on card #322068
which is in slot XZ109 of the Teletype.
Jumper Result
A-OUT
B-OUT
C-IN
D-OUT
E-OUT
F-OUT
G-OUT
L-OUT
H-IN
Y-IN
K-OUT
M-OUT
These keep EOT's and Alarms from disconnecting
the terminal.
Makes motor power follow
DATA SET READY lead.
Configures OUT OF SERVICE
switch to act as ON/OFF
switch for DATA TERMINAL READY.
Keeps terminal in PROCEED Mode
when ON-LINE.
Prevents sending a BREAK on Parity Error.
Enables sending BREAK manually.
42 9/72
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Report No. 2277
Bolt Beranek and Newman Inc.
TELETYPE MODEL 37 (Page Two)
In order to have the OUT F SERVE switch control the motor
power, it is necessary to connect DATA SET READY to DATA TERMINAL
READY on the LIU card. Table TTY 37-1 shows the connection
which produces this configuration.
Operation'
When the teletype is connected in this way, the OUT OF SERVICE
button has the effect of a POWER switch for the motor circuitry.
The logic is, however, always ON. Therefore, when the OUT OF
SERVICE light is ON, the TTY is OFF. Pushing the OUT OF SERVICE
button will turn the motor on, and initiate "hunt mode in the
TIP (if enabled). Pushing that button again disconnects the
Teletype, and turns off the motor.
Special Characters:
CONTROL D (EOT) - This reinitializes the Teletype, but
does not disconnect it from the TIP.
CONTROL N (SO) - This disables printing.
CONTROL 0 (SI) - This enables printing.
Comments'
In this configuration, this terminal can still be used over 103
modems.
Full-half duplex options may be selected by straps on card #322062
which is in location XZ107.
43 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
TELETYPE MODEL 37 (Page Three)
Dedicated HALF-DUPLEX:
Dedicated FULL-DUPLEX:
LINE CONTROL OPERATION:
A-IN, -OUT, C-OUT
A-OUT, B-IN, C-OUT
A-OUT, B-OUT, C-OUT
In addition, the "STUNT" box must be correctly wired--this is
a Teletype Corp. operation.
44 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
TELETYPE MODEL 37 (Page Four)
TABLE TY 37-1
LIU Pad Configuration for Model 37 TTY
EIA LIU
PIN PAD
7
8
9
10
11
12
13
14
15
16
18
19
2O
21
22
23
24
25
E1
E3
E2
E5
E4
E8 - Both EIA pin 6 and pin 20
connect to E8. This is the
only change to a "T" LIU
card.
E?
E20
Eli
El2
El3
El6
El7
El4
El5
E6
E8 - See EIA pin 6.
E25
E24
45 9/72
-----------------------------------------------------------
ASCII CODES (Octal)
21 22 23 24 25 26 27 30 31 32 33 34 35 36 37
"@' I"H .... P .... x" SPA!( _0 8 @ H P X ' h p x
NUL BS DLE CAN -CE
"A .... I .... Q .... Y" ; ) 9 A i Q Y a i q y
SOH HT DCl EM
"B" "J .... R .... Z .... * 2 : B J R Z b j r z
STX LF DC2 SUB
,,C .... K,, ,,S .... [,, # + 3 ; C K S [ c k s {
ETX VT DC3 ESC
,,D .... L .... T .... \. $ . 4 < D L T \ d 1 t J
EOT FF DC4 FS
,, E .... M R .... U .... ]" % - 5 = E M U ] e m u }
ENQ C NAK GS
,, F .... N .... V .... + ,, & 6 > F N V + f n v m
ACK SO SYN RS
"G .... 0 .... W .... " ' / 7 ? G 0 W g o w RUB
BEL SI ETB US .gUT
"X" means Control and X
Code 'Rate (baud)
0 illegal
1 75
2 i10
3 134.5
4 150
5 3OO
6. 600
7 1200
10 1800
1i 2400
12
13
z4
16
17
4800 (output only)
9600 (output only)
19.200 (output only)
i'1!egai
illegal
,external clock
-----------------------------------------------------------
MESSAGE
PROCESSOR
Specification.s for the
ß Interconnect ion of Terminals
and the Terminal
IMP
:, ;.l" '"d;.k?i''.4.f,:; , ".' '; .. '"
??,,',. :,;i(¾2';;::½..;',',.':' ,'.Developed for - ß ,
..... P, ',.'"',. , ';,c,' ,' " ß
:, .',,.,,.,.,.,..,,;-..,-,., ,. 'the Advanced Research. Projects
,:,..,...,,,,-:,.,.,.,,...,,,,,,,..,...:. ,,,bv .Bolt Bera.a,e., and.New&J.nC.,.
-----------------------------------------------------------
, .... Pin Number
6
' 20
EIA RS 232 iNTERFACE CONNECTION PIN ASSIGNMENTS
Circuit Description
AA Protective Ground
BA Transmitted Data
BB Received Data
CA Request to Send
CB .Clear to Send
CC
AB
CP
SCF
SCB
SBA
DB
SBB
DD
SCA
CD
CG
CE
CH/CI
Data Set Ready
Signal Ground (Common Return)
Received Line Signal Detector
(Reserved for Data Set Testing)
(Reserved for Data Set Testing)
Unassigned
Sec..Rec'd. Line Sig. Detector
Sec. Clear to Send
Secondary Transmitted Data
Transmission Signal Element Timing
(DCE Source)
Secondary Received Data
Receiver Signal Element Timing
(DCE Source)
Unassigned
Secondary Request to Send
Data Terminal Ready
Signal Quality Detector
Ring Indicator
Data Signal Rate Selector
(DTE/DCE Source)
l?::-;,.' ß 24 DA Transmit Signal Element Timing
";.k,-.. (DTE Source )
,'";:;.'.:,t,.,.".' :: ,'<.;. .t .. .... -. ...: '--.v.,;' ,",.' .,'. ,', ,,,}',{.'.,',,,H'{"{.:-'%s;t¾},: .}
-----------------------------------------------------------
Report No. 2277
NIC No. 11625
Bolt Beranek and Newman Inc.
SPECIFICATIONS FOR THE INTERCONNECTION OF TERMINALS
AND THE TERMINAL IMP
R.D. Rettberg
Sponsored by:
Advanced Research Projects Agency
ARPA Order No. 1260
Contract No. DAHC15-69-C-0179
6/73
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Report No. 2277 Bolt Beranek and Newman Inc.
Line Interface Units may only be removed
by BBN or Honeywell personnel. If you
believe that a change to the patch panel
of the LIU is needed, contact BBN.
iii 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
TABLE OF CONTENTS
PAGE
1. INTRODUCTION ...................... 1
1.1 Terminals Which Can Be Connected to the TIP .... 1
1.2 Connection of Terminals to the TIP ........ 1
1.3 The User's Point of View on Terminal Connection 3
2. DESCRIPTION OF TIP HARDWARE AND SOFTWARE ........
2.1 General Hardware Considerations .......... 5
2.2 Data Flow in the MLC ............... 9
2.2.1 Input ................... 14
2.2.2 Output ................... 14
2.3 Software Description ............... 18
3. TERMINAL/TIP INTERFACE SPECIFICATION .......... 19
4. MODEMS ......................... 25
4.1 Half-Duplex Modems ................ 25
4,2 Synchronous Modems ................ 26
4.3 103 Modems .................... 26
APPENDIX A: STANDARD LIU CARD CONFIGURATION ........ 29
APPENDIX B: TERMINALS WHICH HAVE BEEN CONNECTED TO A TIP .35
EIA RS 232 INTERFACE CONNECTION PIN ASSIGNMENTS inside front cover
ASCII CODES (Octal) ............... insioe back cover
v 6/'73
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Report No. 2277 Bolt Beranek and Newman Inc.
1. INTRODUCTION
The ARPA Network provides the capability for geographically
separated computers called Hosts to communicate with each other
and with a wide variety of terminal devices. Each Host com-
puter is connected to the ARPA Network through a small computer
which is called an Interface Message Processor (IMP). Terminals
are connected to the ARPA Network through a Terminal IMP (TIP)
which consists of an IMP and a Multi-Line Controller (MLC). A
typical node on the ARPA Network is shown in Figure !-I.
This document contains the information for connecting terminals
and modems to the TIP.
1.1 Terminals Which Can Be Connected to the TIP
Appendix B provides a description of the terminals which have
been successfully connected to the TIP. If it is desired to
connect a terminal which is not described in Appendix B, consult
Section 3 for the terminal specification. Terminals which violate
the software specification (Table 3-1) may also be connected by
appropriate software modifications. Be certain to contact BBN
early if software modifications are necessary.
1.2 Connection of Terminals to the TIP
The sections listed below describe the details of Terminal Inter-
facing. In many cases, this detail will not be necessary for
connecting your terminal to the TIP.
ß If your terminal is described in Appendix B, follow the
relevant suggestions.
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\
\
\
\
\
i 2
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ß If your terminal has a 25-pin plug, try plugging it
into an LIU (located at the bottom of the TIP) which
has a "T" label. If this works, set the terminals
rate to 110, 150, or 300 baud, and type E. HELLO
means that you are connected. Refer to the User's
Guide to the Terminal IMP, BBN Report No. 2183.
If these methods fail, you should consult the following sections
of this manual:
Section 2 gives a brief description of the configuration of a
TIP. The subsection on data flow in the MLC (2.2) may help you
determine the problem by means of the display console indicators.
Section 3 gives specifications for terminal connection.
studying this you may be able to determine what is wrong.
Section 4' discusses modems.
Through
If you succeed in connecting a terminal which is not listed,
please let us know in some detail how it was done, and how well
it works. Please contact:
Network Control Center
Bolt Beranek and Newman Inc.
50 Moulton Street
Cambridge, Massachusetts 02138
The same address may be used for obtaining further information.
1.3 The User's Point of View on Terminal Connection
It is strongly suggested that anyone intending to connect terminals
to the TIP, as well as anyone wishing to know how the TIP is used,
read the User's Guide to the Terminal IMP, BBN Report No. 2183.
3 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
The topics of particular interest in connectimg terminals are'
ß The Network Virtual Terminal
ß Typical Uses of the TIP
ß Echoing
ß Break
ß "Unusual" Uses of the TIP
ß Device Parameters
ß Setting Another Terminal's
Parameters
ß The DIVERT OUTPUT Command
Line Interface Units may only be removed
by BBN or Honeywell personnel. If you
believe that a change to the patch panel
of the LIU is needed, contact BBN.
4 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
2. DESCRIPTION OF TIP HARDWARE AND SOFTWARE
A functional diagram of the BBN TIP hardware is shown in Figure
2-1. The TIP consists of two major assemblies: the basic H316
IMP, and the Multi-Line Controller (MLC). The IMP section per-
forms the message handling functions of a node in the network,
and provides additional processing power for the MLC. Informa-
tion on the basic IMP section may be found in BBN Report No. 1877.
The MLC section is described in detail in BBN Report No. 2184.
The MLC consists of Common Logic, and Line Interface Units (LIU) o
Each LIU services an input and an output on the TIP. Terminals
and modems are connected to these ports. Up to 63 LIU's may be
installed in the TIP. As one option, a rack of up to 16 modems
may be mounted inside the TIP enclosure.
A photograph of a TIP is shown in Figure 2-2 which indicates the
location of these assemblies. The option drawer above the main
.processor contains additional network (as opposed to terminal)
modem interfaces and Host interfaces. The H316 main frame
drawer houses the basic processor. The MLC drawer is immediately
below the processor, and holds the MLC common logic. On the
front of this drawer is the MLC console. At the bottom of the
TIP is the LIU rack, which holds the LIU cards.
Throughout the remainder of this section, we will not make any
effort to distinguish between the contributions of the LIU and
the Common Logic to a port's function.
2.1 General Hardware Considerations
Data Fommat - The MLC hardware data format is bit serial with
characters framed by start and stop bits:
5 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
50 KBPS
COMM LINES
l0 KBPS
TO LOCAL
HOST
I MODE M
INTERFACE
MODEM
INTERFACE
I HOST
INTERFACE
ß --J-, ,
EXTERNAL
LOW SPEED
MODEM (UP
TO 9.6 KBPS)
EXPANDED H516 IMP
MULTI-LINE
HIGH SPEED
DMC
16 CHANNEL
I
!l l
H316
PROCESSOR
H316
ZO K CORE
CONTROLLER
COMMON I
LOGIC
LOCAL
TERMINAL
I LOCAL I
TERMINAL
1
UP TO 65 LINE
INTERFACE UNITS
FIG. 2-1
BBN
TIP HARDWARE
CONFIGURATION
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I
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Report No. 2277 Bolt Beranek and Newman Inc.
+,SPACE
- MARK
START
BIT LSB
PARITY
MSB BIT
0 1 0 0 0 1 1
5 3
Compatible ASCII Capital E
STOP BITS
The number of data bits may be from 5 to 8 as determined by the
parameter SIZE'
NUMBER OF
SIZE DATA BITS
o 5
3 8
$iga œeuels - All the signals at the EIA connector of an LIU
are EIA compatible, and interpreted in this way:
Data Signals
-25-----------------------------
Report No. 2277 Bolt Beranek and Newman Inc.
Code Rate (baud)
0 illegal
i 75 -
2 110
3 134.5
4 150
5 300
6 6OO
7 1200
!0 1800
i1 2400
12 4800 (output only)
13 9600 (output only)
14 19200 (output only)
15 illegal
16 illegal
17 external clock
2.2 Data Flow in the MLC
Block diagrams of the Input and Output data paths are shown in
Figures 2.2-3 and 2.2-4. Except for the common logic and H316
Mainframe, the Input and Output circuitry are independent. The
LIU pads referred to in these figures are shown in Appendix A.
The fields marked by asterisks are shown on the MLC console.
For example, the MSTAT bits are labeled in this manner:
MSTAT
IO 0 0 0 0 0
1 2 3 4 5
(light on indicates 1)
The fields BOUTDAT, BINDAT, SIZE, INRATE and OUTRATE have the
least significant bit on the right.
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The upper half of the MLC console is associated with the central
logic which is common to all lines. The lower half displays the
status of an individual line. The lne to be displayed is selected
by entering the line number into the LINE SELECT switches. The
setting of these switches concerns only the display and in no way
affects the internal functioning of the MLC. The line number
(octal) is determined by the slot in the LIU rack into which the
desired LIU is plugged. (Slot 0 is empty.) See Figure 2.2-1.
Most of the user commands in the TIP User's Guide refer to the
decimal equivalent of this line number. Don't get confused.
A diagram of the MLC console is shown in Figure 2.2-2, and the
fields are summarized in Table 2.2-1. Throughout the following
discussion, inversions of the signals are not indicated.
i0 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
I- z
o z
i o
0 (.9
o
o
_l z
o
Jo
u
J
u
__
J
0_
-J
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12 9/72
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Report No. 2277 Bolt Beranek and Newman Inc.
b0 "d
2E ,-.I
O O
,%, O b0
" H
,%,
rd
" O
,%,
rd
O H 2:
H O
,%, O O
d9 ,--I
" O
EL rd 0
ß H 0 'H 4-) :> o 0 4- ¸ 0
¸ q-4 .H E 4-) q-4 rd
¸ .H rd o : rd 4 0
o ,% ,%, 0 i::z, O , ,% o 0
H o H ½Q o H U] o cQ.H CQ 0 ½3 0 (D o
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Report No. 2277 Bolt Beranek and Newman Inc.
2.2.1 Input
The input block diagram is shown in Figure 2.2-3.
section provides these functions:
The input
ß 6 status inputs
ß Input data path
ß Variable input rates
ß External clock
The status inputs (MSTAT through MSTAT5) are direct input paths
which may be read at any time by the processor. Their use will
be described in the subsection on software (2.3).
The input character is assembled in the Input Data Shift Register.
When complete, it is transferred into the Buffered Input Data
Register, from which it is transferred to the mainframe memory.
The character length is determined by SIZE, and the rate by
INRATE. If the rate is specified as octal 17, the clock for the
Input Data Shift Register is taken externally on the path
External Input Clock. The Input Data is captured on ß the
negative edge of the signal on LIU pin El7 or E25. If the Input
Data line is held spacing during the first stop bit of a char-
acter, the line is determined to be breaking, and BRK is set.
The last character received is held in BINDAT.
2.2.2 Output
The output block diagram is shown in Figure 2.2-2.
section provides these functions:
The output
ß 4 control outputs
ß Output data path
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ß Variable output rate
ß External clock
The control outputs (MCBIN through MCBIN 3) are direct output
paths which are controlled by the software. Their use will be
described in the subsection on software (2.3).
The output character is delivered to the Buffered Output Data
Register from the mainframe memory. When the last character
has left the Output Data Shift Register, the next character is
transferred into it from the Buffered Output Data Register; then
the character is shifted out with start and stop bits added.
The rate is determined by 0U7RA7E. If rate 17 (octal) is spec-
ified, the clock for the Output Data Shift Register is taken
externally from the path External Output Clock. The output
data changes on the positive going edge of the signal on LIU
pads El5 and E24.
The last character sent out is held in BOUTDAT.
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STATUS INPUTS
E $ O'
E 6 o
E 8 o
E12 o
E13 o
E16 o
LIU
PAD
E 3 o
El7&
o
E 25
]> *MSTAT
L *MSTAT 1
> *MSTAT 2
> *MS TAT 3
> *MSTAT 4
> ::MS TAT 5
EIA
LEVEL
CONVERTERS
*BRK
Input Data
External Input
Clock
MLC COMMON LOGIC
AND
H316 MAINFRAME
Buffered Input Data
*B I NDAT
Input Data Shift
Register
* I NDAT
I * I NRATE
Clocks
*S I ZE
*MANIFOLD TYPE - Indicates fields which have corresponding
light-emitting diodes on the MLC console.
FIG. 2.2-3
MLC DATA PATH BLOCI' DIAGRAM INPUTS
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MLC COrION LOGIC
AND
H316 MAINFRAME
Buffered Output Data
*BOUTDAT
Output Data Shift
Register
*OUTDAT
*OUTRATE
Clocks
CONTROL OUTPUTS
*MCB I N C
'*MCBIN I
*MCB I N 2
*MCB I N 3
Output Data
EIA
L E VEL
CONVERTERS
External Output
Clock
oEld
. oE19
.,oE 20
LIU
PAD
I
o E 2
El5&
0E24
::MANIFOLD TYPE - Indicates fields which have corresponding
light-emitting diodes on the MLC console.
FIG. 2.2-4 MLC DATA PATH BLOCK DIAGRAM - OUTPUTS
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2.3 Software Description
The TIP software is currently undergoing changes to expand its
capabilities; this subsection describes the way the software uses
the MLC now. The TIP User's Guide should be read for information
concerning software facilities available to the user.
At this time, the software handles the control and status bits
in this way:
ß M$7AT ,1,3,4,5, are ignored by the software.
ß MCBIN ,1,2 are held ON by the software.
ß MCBIN 3 is held ON, except for a short (approximately
1/2 sec.) period following an ON to OFF transition of
M$7AT 2, during which it goes OFF.
ß MSTA7 2 is used by the TIP software to determine that
the terminal is connected to the TIP, and able to
transfer data. If "hunt" mode is enabled for this
device, an ON to OFF transition of this signal initiates
"hunt" mode.
Also, at this time, the software is not capable of keeping out-
put lines full at speeds greater than about 3000 baud.
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3. TERMINAL/TIP INTERFACE SPECIFICATION
This section specifies the interface between a terminal and the
TIP. See Section 4 for connections involving modems. It is
hoped that by examining this section, an engineer will be able
to determine whether he has met the conditions necessary for
proper operation of a terminal connected to the TIP.
To a large extent, the TIP follows EIA Standard RS-232C.
Familiarity with that document is recommended. The pin alloca-
tions specified by that standard are given inside the front
cover.
In order to connect a terminal to the TIP without modems, each
must look like a modem to the other. Input and output connec-
tions are therefore cross-connected at the LIU pads, as shown
in Table 3-1.
Expansions to this specification are planned in the near future
(particularly as this relates to control signals). It is
therefore very important that this section be kept up-to-date
as revisions are provided.
Ooeotor - The connector from the terminal should be equivalent
to a Cinch DB-25P. it is recommended that extension cords for
terminals provide for all 25 pins in order to allow for future
changes.
Signal œvels - All signals are represented by bipolar low
voltage levels. All signals are measured with respect to signal
ground. The source of a signal shall deliver a voltage of
magnitude between 5 and 25 volts into a load of not less than
3000 ohms. The reactive component of the load shall not be
inductive, and the capacitance shall not exceed 2500 pfd. measured
at the interface connector. The signals shall be interpreted in
this way:
Data Signals
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Control & Timing Signals
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Character Code - The TIP software accepts ASCII 8-bit code.
Parity is ignored on input, and undefined on output. IBM 2741
and 2741-1ike devices are handled specially. See Appendix C.
Carriage Return Speed - Carriage return speed is known to be
reasonably compensated for Tetetypes 33, 35, and 37; and,
separately, for Execuport-!ike devices. A line printer (ODEC)
with a small (256-character) buffer is also reasonably compen-
sated. This compensation is set by the TIP program.
Half-Full Duplex - The TIP can handle both half and full duplex
terminals, provided that the half-duplex connection accepts
control signals which are used as indicated in Table 3-1.
Terminals Which Provide Their Own Clock - Terminals which pro-
vide their own clocks for transferring data can be connected to
the TIP provided they meet the previous specifications. The
clocks should be routed to LIU pads El5 and El7. The data
lines should change on the positive edges of the clocks, and
should be sampled on the negative edges.
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EIA
PIN
1
2
LIU
PAD
$3
3 E2
7 E7
8 E20
TABLE 3-1 TIP SIGNAL ALLOCATION FOR TERMINALS*
2O E8
DESIGNATION
(FROM THE POINT OF VIEW OF THE TERMINAL)
PROTECTIVE GROUND (AA) - Used.
TRANSMITTED DATA (BA) - Used for data going from the
terminal to the TIP.
RECEIVED DATA (BB) - Used for data going from the TIP
to the terminal.
SIGNAL GROUND (AB) - Used.
RECEIVED LINE SIGNAL DETECTOR (CF) - Modem control bit 3.
Held ON by the TIP, except for a short (approximately
1/2 sec.) period following an ON to OFF transition of
DATA TERMINAL READY, during which it goes off.
DATA TERMINAL READY (CD) - Modem status bit 2. THIS SIGNAL
IS USED BY THE TIP to determine that the terminal is
connected to the TIP. If "hunt" mode is enabled for
this device, an ON to OFF transition of this signal
initiates "hunt" mode.
The following control signals are held on by the TIP software:
5 E4 CLEAR TO SEND (CB) - Modem control bit . Held ON by
the TIP.
6 E!9 DATA SET READY (CC) - Modem control bit 2.
the TIP.
16 E!4 SECONDARY RECEIVED DATA (SBB) - Modem control bit 1.
ON by the TIP.
Held ON by
Held
The following status signals are ignored by the TIP software:
4 E5 REQUEST TO SEND (CA) - Modem status bit . Ignored by
the TIP.
12 El2 SECONDARY RECEIVED LINE SIGNAL DETECTOR (SCF) - Modem
status bit 3. Ignored by the TIP.
13 El3 SECONDARY CLEAR TO SEND (SCB) - Modem status bit 4.
ignored by the TIP.
14 'E!6 SECONDARY TRANSMITTED DATA (SBA) - Modem status bit 5.
Ignored by the TIP.
19 E6 SECONDARY REQUEST TO SEND (SCA) - Modem status bit 1.
Ignored by the TIP.
*This configuration makes the LIU look approximately like
a 103 modem to the terminal.
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4. MODEMS
It is desired that the TIP be able o operate with terminals over
private or leased lines, or over the switched telephone network.
This requires the use of a pair of modems between the terminal
and the TIP. At the present time, only one such modem (Bell 103,
or equivalent) is supported by the TIP software. We expect to
be able to support 202-equivalent modems (with reverse channel)
in the future.
If may be that a group desiring to use another type of modem
could coax that modem to work within the available software and
hardware structure. For that purpose, this section will try to
describe the difficulties in using half-duplex modems, the use
of synchronous modems, and the manner in which the 103 modem is
supported.
4.1 Half-Duplex Modems
Half-duplex modems are modems in which data on the primary data
channel can flow in only one direction at a time. Data cannot
flow both ways at the same time. There may or may not be a
"secondary" or "supervisory" channel which points in the direction
opposite the primary channel. The essential problem involved in
half-duplex operation is control of the direction of data flow
on the primary channel. Significant questions are:
ß What protocol should be adopted for turning the line
around--special control characters, or use of a
secondary channel?
ß Which end (if either) is in control of the channel?
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ß If the terminal is receiving a large listing, how
can the user terminate the output when the channel
is pointing the wrong way?
Who should do the echoing and when?
These problems are clearly a matter of convention. Unfortunately,
EIA Standard RS-232, which many modems follow, does not define
a convention which would answer these questions. It is very
helpful if a request to BBN for a modem on the TIP includes a
statement of what terminals are to be connected to the other
end, and what convention they follow.
4.2 Synchronous Modems
Synchronous modems normally do not use the character format shown
in Fi.gure 3-1. Such a connection to the TIP does not work. However,
the TIP should be able to use synchronous modems provided that
the characters are framed by start and stop bits, and that the
synchronous modem is similar enough to a modem which is supported
by the software. The device rate must be set to 17 octal through
the use of @ DEVICE RATE 123. This disables Hunt mode, therefore
when this modem is disconnected from the LIU, remember to re-
enable "hunt" mode with @ DEVICE RAIE 4534 (for example). See
TIP User's Guide.
4.3 103 Modems
Description:
The Bell Telephone 103 modem is a low-speed (up to 300 baud),
asynchronous, full-duplex modem for use on private leased lines
or the switched telephone network.
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Connection'
See Table 4.3-1 for the pin connecHion on the LIU card, and for
a description of the TIP's use of the signals.
Operation ß
In use, the modem at the TIP end is usually left in the AUTO
mode. When a user wishes to connect his terminal, he dials the
number of the modem at the TIP. After the ring is answered and
a data carrier is heard, the user depresses the DATA button. The
user is then connected as if his terminal were connected directly
to the TIP. He types the characteristic character for his
terminal, receives HELLO, and proceeds to use the network as
desired.
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EIA LIU
PIN PAD
1 E1
2 E2
3 E3
5 E5
7 E7
8 E8
20 E20
TABLE 4,3-1
TIP SIGNAL ALLOCATION FOR 103 MODEM
PROTECTIVE GROUND (AA) - Used.
TRANSMITTED DATA (BA) - Used for data going from
the TIP to the MODEM.
RECEIVED DATA (BB) - Used for data going from the
MODEM to the TIP.
CLEAR TO SEND (CB) - Modem status bit . Ignored by
the TIP.
DATA SET READY (CC) - Modem status bit 1. Ignored
by the TIP.
SIGNAL GROUND (AB) - Used.
RECEIVED LINE SIGNAL DETECTOR (CF) - Modem status
bit 2. This signal is used by the TIP to deter-
mine that a connection has been made. If "hunt"
mode is enabled for this device, an ON to OFF
transition initiates "hunt" mode.
DATA TErmINAL READY (CD) - Modem control bit 3.
Held ON by the TIP, except for a short (approximately
1/2 sec.) period following an ON to OFF transition
of RECEIVED LINE SIGNAL DETECTOR. This disconnects
the telephone line in preparation for the next call.*
All other signals are connected as shown in Appendix A
but are not used by the 103 modem.
*It should be noted that if the carrier is lost for a short time,
a disconnect is initiated. Also, if the carrier is not detected
(for example, by a voice call) no disconnect will occur.
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APPENDIX A
STANDARD LIU CARD CONFIGURATIONS
FOR TERMINALS AND MODEMS
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STANDARD LIU CARD COIlFIGURATIONS FOR TERMINALS AND MODEMS
In order to provide the necessaryflexibility in assigning the
pins on the EIA (DB-25P) connector to the various inputs and
outputs of the LIU, a patch panel is provided on the LiU card.
The pin assignment is shown in Figure A-1.
Table A-1 shows the interconnection necessary to configure the
LIU to drive terminals or modems.
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