PDP11 PeripheralsHbk 1972 - Trailing-Edge

In addition, the M798 module allows the UNIBUS to be driven by standard open
collector TTL gates. The inputs to each M798 driver circuit are pulled to + 5V
through a 1 kn resistor. As shown in Figure 2·9b, an internal wire·ORed bus is
created that is driven from standard open collector gates (available on M141 and
M149 modules) or from UNIBUS drivers (available on M783 UNIBUS Transceiver
modules). The driver input loading is 4.1 TTL loads for each of the 16 inputs. The
output drive signal for each of the 16 outputs is 50 mA sink at 0.8V maximum.
The open collector leakage is 25fL A. A circuit schematic of the M798 UNIBUS
Drivers module is shown in Figure 2-10.
REG A BIT n
REGBBITn
REG C BIT n
+5V
1 k.n.
Figure 2-9 a. One of 16 Circuits on the M798
+5V
.-'- INTERNAL BUS
Figure 2-9 b. Typical Use of M798
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