Section I. General Description; General - Texas Instruments 990 Maintenance Manual

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945407-9701
SECTION I
GENERAL DESCRIPTION
1.1 GENERAL
The 16 Input/16 Output TTL Data Module (see figure 1-1) provwes a two-way communication
path between a Texas Instruments 990 Computer and attached peripheral devices which are
operated by or which genernte TTL level digital signals.
l he
module may be used in any
Communications Register Unit (CRU) port within the CPU chassis, or it may be used in a CRU
expansion chassis.
The module provides 16 input and 16 output lines. Each line may be addressed as a single
independent binary value or as a member of a group of from 2 to 16 lines" Alternate versions of
the module provide 15 normal inputs, 14 normal outputs, an interrupt line, and an interrupt
mask. Data module inputs and outputs are negative logic levels that switch between 0 volts and a
positive voltage level. Each output is an open collector transistor capable of sinking up to 50
milliamperes at up to 30 volts. Pads are available on the module for installing pull-up resistors or
resistor divider networks at each output of the module. Each input is connected to the base of
an emitter-follower transistor that operates at TTL levels. Pads for input filter capacitors are also
available on the module.
Use of the data module in a simplified control system is shown in figure 1-2. In this example,
the computer and the data module combine to sense the level of fluid in a storage tank and to
control the operation of an input valve to
reference levels. When the fluid reaches one of the prescribed references, an interrupt and an
FLOW IN*
OPEN!CLOSE
OPEN/CLOSE
r
VALVE
VALVE
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r
U I
I
VALVE
I
161/0
DATA
MODULE
I
MODEL
TANK FULL
990
I
COMPUTER
I
INTERRUPT
STORAGE
TANK
TANK FULL
I
FLOW
TANK LOW
L OUT
*FLOW IN
>
FLOW OUT
(A)129473
Figure 1-2. Simplified Control System Example
1-1
Digital Systems Division