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|  MIL-D-81347C(AS)
Digital Output Multiplexer
3.5.1.4.2
Functional Description - The Computer is capable of servicing
3.5.1.4.2.1
16 output peripheral equipments which utilize the normal output data transfer. The DPS contains more
than 16 output peripherals; however, the rate and priority of the data from many of these peripherals
do not demand realtime access to the computer memory; i.e., many of the output peripherals can
communicate with the computer via a buffer unit. In the DPS, this common output buffer is termed
the Digital Output Multiplexer (DOM). Figure 5 is a functional flow diagram for the DOM.
General Description - The DOM shall provide the capability of
3.5.1.4.2.2
transmitting up to 12 data bits from the computer to each of 16 output peripherals via a single computer
output channel. The operation of the DOM shall be independent of the DIM except for test loops.
Operating Requirements
3.5.1.4.2.3
Data Transfer - Computer to Peripheral Equipment via Digital
3.5.1.4.2.3.1
Output Multiplexer - The computer shall be able to output one 12-bit data word to one of the 16 periph-
.
eral equipments by following the control sequence given below:
(1) The computer program initiates a normal output buffer for
the channel assigned to the DOM.
(2) The DOM sets the Output Data Request line indicating that it
is in a condition to accept data.
(3) The computer 1/0 subunit detects the Output Data Request.
(4) The computer, at its convenience, places 12 data bits and
4 address bits (identifying the peripheral equipment to receive the data) on 16 computer data lines.
(5) The DOM transmits the 12 data bits to each of the 16 periph-
eral units.
(6) The computer sets the Output Acknowledge line, indicating
that the data is ready for sampling.
(7) The Digital Output Multiplexer decodes the address and
transmits the Output Acknowledge signal to the peripheral equipment specified by the address code.
(8) The peripheral equipment, upon receipt of the Output Acknowl-
edge signal from the DOM, samples the 12 data lines.
(9) The Computer drops the Output Acknowledge.
(10) The DOM drops the Output Acknowledge to the peripheral
equipment, indicating that the period for sampling the data is terminated.
Timing - The DOM shall be capable of processing one computer
3.5.1.4.2.3.2
output word every 10 microseconds.
3.5.1.4.2.4
Test Loops
In-Flight Performance Monitoring Channels - Two of the channels
3.5.1.4.2.4.1
(5 and 10) of the DOM shall be designated as test channels. When the computer program addresses
these channels, the 12 data bits accompanying the test channel addresses shall be stored in the DOM.
When the data is stable, the DOM shall set the Enter line of the DIM channel corresponding to the test
channel addressed by the computer; i.e. , if the computer transmits data to channel 5, the DOM shall
set the Enter line and transmit the stored data on the DIM channel 5 input data lines; the Enter line and
data shall be reset when a Channel Input Acknowledge signal is received from the DIM: the same proce-
dure shall be followed for DOM channel 10. This loop operation, computer to DOM to DIM to computer,
shall permit the computer program to monitor automatically the performance of the DOM and DIM.
The test loops shall be utilized for in-flight performance monitoring and diagnostic programs.
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