PDP11 PeripheralsHbk 1972 - Trailing-Edge

2.2.1 UNIBUS Cables
UNIBUS Jumper Module M920- The M920 Module (see Figure 2-4) is a double
module that connects the UNIBUS from one system unit to the next. The printed
circuit cards are on one-inch centers. A single M920 Module carries all 56 UNI­
BUS signals and 14 grounds.
UNIBUS Cable BCllA . The BCllA (see Figure 2-5) is a l20-conductor Flexprint
cable used to connect system units in different mounting drawers or to connect a
peripheral device removed from the mounting drawer.
The 120 signals include all the 56 UN IBUS lines plus 64 grounds. Signals and
grounds alternate to minimize crosstalk. Cable types and lengths are listed below:
Type
BCllA-2
BCllA-5
BCllA-8f
BCllA-lO
BCllA-15
BCllA-25
Length (ft.)
2.0
5.0
8.5
10.0
15.0
25.0
2.2.2 UNIBUS Terminations
The M930 UNIBUS Terminator Module is a short, double-size module that terminates
all signal lines on the Unibus. This module requires 1.25 amps at 5v. All
pins have a resistive divider termination of l80n to + 5v and 390n to ground, except
those listed below:
390Qin
parallel with
0.001 }JJ to + 5
(for AC LO, DC LO)
BFl
BF2
l80n to + 5V
(for grant lines)
AVI
AUI
BAI
BEn
BE2
AB2
AC2
ANI
API
ARI
ASI
AT!
AV2
Ground Pins
BB2
BC2
BDI
BEl
BTl
BV2
+ 5V Input Pins
2.2.3 UNIBUS Receivers and Transmitters
Various bus driver and receiver modules may be used in interfaces to provide signallevels
compatible with the UNIBUS. These modules (M783 , M784,M785, and
M798) are discussed separately in the following paragraphs.
2.2.3.1 M783 UNIBUS Transmitter - This transmitter module contains 12 drivers;
8 drivers have a common gate line, 4 have 2-input positive AND gating. Input
loading is 1.25 standard TTL load. The module is a single-height, 8.5 inch-long
Flip-Chip. A circuit schematic of the M783 Transmitter is shown in Figure 2-6.
206
AA2
BA2