Table of Contents
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FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - - -
External Interface Specification
The available ports for open-ended development are the ports labeled ALM, UPS, EXT2, and EXTl.
Each of these ports is a 6-pin (4 equipped) modular, plug-type connector. The input ports are
designed to support Transistor-Transistor-Logic (TTL) driven inputs or relay closure type inputs. Power
should be removed from the 3B2 computer before a connection is made to any of these ports. Since the
ports are sensitive to state changes, connecting cables while the power is present can cause erratic
system behavior, even system panics.
The following table shows the interface specifications for the external interface ports.
PORT LABELS
ALM
UPS
EXT2
EXTl
Direction
Output
Input
Input
Input
Current
Sink 35ma max
Source 2ma max
Source 2ma max
Source 2ma max
VCE: 1.0v at 35ma
Voltage
0.8v at lOma
VIL
=
0.8v max
VIL
=
0.8v max
VIL
=
0.8v max
0.7v at 5ma
VIH
=
2.0v min
VIH
=
2.0v min
VIH
=
2.0v min
VCE: 30v max
VIH
=
7.0v max•
VIH
=
7.0v max*
VIH
=
7.0v max•
VEC: 7.0v max
Active State
Conducts
Logic Low "O"
Logic Low "O"
Logic Low "O"
Signal Duration
127ms min
20ns min (low)
20ns min (low)
20ns min (low)
Pl
Darlington Emitter:j:
Ground
Ground§
Ground!!
(MJOUTl)
Pint
P2
Darlington Collector:j:
AC FAILURE
EXTERNAL TTL§
EXTERNAL TTL!f
(MAJOR!Nl)
(ACFSETO)
(EXT21NO)
(EXTlINO)
Signals
P3
Darlington Emitter••
Ground
Ground
Ground
(MINOUTl)
P4
Darlington Collector••
LOWBAT
NC
NC
(MIN!Nl)
(LOWBSETO)
LEGEND:
NC -
No Connection.
• -
Absolute maximum rating over a free-air temperature range of O to 70 degrees C.
t -
Pl is on the right and P4 is on the left of each modular jack, referenced with the
component side up and the face plate toward you.
:j: -
Major alarm outputs (intended for activating an External Alarm Processing Unit).
§ -
Closure across these pins results in major alarm (accepts either TTL or Closure).
