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Gemini User's Manual
The groundings are provided by three pins. Pin 16 is the signal
ground, 17 is the chassis ground, and pin 33 is the external ground.
Pin 18 carries 5 volts of direct current.
Twisted-pair return signals for pins 1 through 12 are conveyed
by pins 19 through 30, respectively.
Pin 31, INPUT PRIME, carries the signal for resetting the
control logic. When this signal goes low, the printer is initialized
and the memory buffer is cleared. Another output signal, ERROR,
is carried by pin 32. When Gemini is off-line or disabled by an
abnormal state, the ERROR signal goes low.
Pins 14, 15,34,35, and 36 are unused.
Signal Name
Circuit Example
Input
DATA 1-8
4.7 k.Q ~
74LS compatible
~
STROBE
~
74LS compatible
4.7~~
470pF
~
Output
4.7
okQ-j
~
compatible
BUSY,ACK
Figure N-2. Sample circuit for parallel interface.
ACK
DATA
STROBE
BUSY
,
1
1
: . - Approx .
.......!--
Approx. ~
:
9 I(see.
I
9 II.sec.
I
, ,
L -_ _ _ _ _ _ _ _ _ '
....JI
T
=
more
than 0.5
~sec.
Figure N-3. Data-transfer timing chart for parallel interface.
248
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