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|  MIL-D-81347C(AS)
MDM Status Signals - In addition to the power error, track error
3.5.4.4.4.3.3.4.6.6
and clock error status signals defined in other paragraphs within the MDM section of this specification,
the Magnetic Drum Memory shall provide the status signals defined in the following paragraphs.
(1) Temperature Error Status - The Magnetic Drum Memory
shall have a device to detect a warning overtemperature condition in the drum subassembly. The
warning overtemperature threshold of the sensor shall be selected such that any additional data proc-
essing (writing or reading) after an overtemperature indication could result in erroneous operation as
a result of the increased temperature in the drum subassembly.
During a warning overtemperature condition the tempera-
ture error status line shall indicate an open-circuit condition at all times that a warning overtemperature
condition exists. Whenever the temperature comes within the reset tolerance of the sensor, the
temperature error status line shall automatically recover and indicate a Logic 1 level.
This signal shall be sent to the Drum Controller and shall
be defined as the MDM temperature error status signal.
(2) Temperature Shutdown Status - The Magnetic Drum
Memory shall have a device to detect a critical overtemperature condition in the drum subassembly.
The critical overtemperature threshold of the sensor shall be selected such that any further operation
of the drum subassembly after a critical overtemperature indication might subject the drum sub
assembly to mechanical/electrical damage.
The sensor shall be normally open whenever the tempera-
ture is below the critical temperature limit and shall close whenever the critical temperature limit is
exceeded. Whenever the temperature falls below the reset temperature limit of the sensor, the sensor
shall automatically revert to a normally-open condition. Upon receipt of the critical temperature indi-
cation Logic Unit 4 shall automatically remove AC power from the MDM.
In the closed position, the sensor shall have a maximum
resistance of O. 5 ohms and shall be capable of conducting 300 milliamperes continuously without
damage. Both interface lines (MDM Temp Sht Dn and MDM Temp Sht Dn Ret) shall be isolated from
the MDM chassis and MDM signal ground. This sign al shall be sent to the Drum Controller and shall
be defined as the MDM temperature shutdown status signal.
Speed Error Status - Whenever the MDM power error
(3)
status line is a Logic 1 level, the MDM shall have the capability of detecting an out-of-tolerance drum
speed condition or other normal operation speed related conditions which would inhibit write/read
operations from being performed and provide a Logic 1 level on the MDM speed error status line as
long as the condition exists. This signal is known as the MDM speed error status signal. A stable
speed error status Logic 1 level shall be provided to the Drum Controller from the time the MDM
power error status line becomes a Logic 1 to the time the drum speed error status line becomes a
Logic O level.
(4) Pressure Error Status - The Magnetic Drum Memory
shall have the capability of detecting an internal drum pressure error and provide a Logic 1 level as
long as the pressure error exists. This signal is known as the MDM pressure error status signal.
3.5.4.4.4.3.3.4.6.7
Interface Logic Levels - Except as noted, all signal transmission
between the MDM and the Drum Controller shall be digital in nature and conform to the following defi-
nit ions. (All voltage levels specified are referenced to signal ground. )
(1) Logic 1 Level - Logic 1 signal level is defined as the
region -2.0 VDC to +2.0 VDC except that the -2.0 VDC ( excursion from O VDC) shall be limited to a
maximum of 200 nanoseconds. Unless stated otherwise, a Logic 1 signal level indicates that the
signal is true.
(2) Logic O Level - Logic O signal level is defined as the
region from +3.0 VDC to +7.0 VDC. Unless stated otherwise, a Logic O signal level indicates that
the signal is false.
269
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