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A12
Al2
Front-Panel
Interface,
Circuit
Description
Al2 Front-Panel Interface contains the miscellaneous digital functions for interfacing with the
Al5 Controller.
Keyboard Matrix
@
The
keyboard is organized as a matrix (rows and columns) of normally open SPST switches.
The rows are driven by U2 and U3. U6 functions as a key-down detector. Q2 and associated
circuitry
debounce
the key switches, and
U14B
latches the key-down condition.
Ul
and U4
gate the key columns onto the Data Bus. By selectively enabling the key rows, Al5 Controller
can poll the keyboard.
Oven
Cold
Sensor
@
When U22 senses the oven line is less than
+17
V, it tells the Controller that the oven is no
longer cold.
Rotary
Pulse
Generator
(RPG)
Control
@
UllB
enables the RPG, allowing the pulses to be counted.
UllA
detects the direction of
rotation of the RPG (rotation of the DATA knob on the front panel).
U18
and
U19
count the
number of RPG pulses since the last RPG RESET. U28 provides a
holdoff
of about 200 ms,
until service is requested, giving the instrument time to respond to the last request and to
continue to sweep before the next request occurs; that is, to give the operator visual feedback.
Service
Request
@
This circuit encodes the various requests for service for the Al5 Controller.
U24 encodes the service request. U27 is a change detector (HXRF or LRMT), and U25
latches these changes. U14A detects and latches the falling edge of HSWP.
U13 also provides the reset pulses for clearing the request latches U14A, U14B, U16A, U25A,
and U25B.
U16B
is cleared by any pending request (that is, it restarts Al5 Controller) by
U24.
Q3 pulls HSWP low whenever a request is pending.
U12 gates the encoded request and also places HXRF or LHBZ on the Data Bus.
Al2
1