Specifications

CONSTRUCTION
Fig. 4: Schematic circuit of special display system
(i)
Fig. 5: Flowcharts for the main program and various subroutines
(ii)
(iii)
1. Q1 (logic 1) à SW2 à R14 à internal
LED (IC6) à slot-2 à base lead à BC junction
à collector lead à slot-3 à D1 à SW3 à Q2
(logic 0)
2.
Q1 (logic 1) à SW2 à R14 à internal
LED (IC6) à slot-2 à base lead à BE junction
à emitter lead à slot 1 à D5 à SW1 à Q0
(logic 0)
Thus, only the internal
LED of IC 6
would start flickering, and the data that
would be formed at the emitters of the
transistors is also
010. Accordingly, the
base-Id that would be developed in this
case is
0000 0010=2(H).
Since, under the same orientation of
the transistor in the socket, the base-Ids
are different for a pnp and an npn device,
the software can decode the type of the
device.
In a similar way we can justify the
production of the other base-Ids, when
their collector, base, and emitter are in-
serted in the testing socket differently.
Once the base-Id is determined, the
software sends the same number for a
pnp-device (here=
05(H)) through port C
(port number 83), with the bit format
shown in Table V.
As a result, the control input of
SW2
(pin 12 of IC5) gets logic 0. So the switch
opens to insert resistor
R5 in series with
the base circuit. This action is neces-
sary to identify the emitter (and hence
the collector) lead as described earlier
under ‘Principle’ sub-heading.
On the contrary, since an npn-de-
LT543
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