Page 330 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c05
316 MECHATRONICS Printer: Yet to Come October 28, 2014 11:15 254mm×178mm
Decoder
CPU Address
bus
5 V
IN
Control
bus
Data DI Q R
bus
Q S
R-S
Flop-flop
5 V

Decoder
CPU Address
bus

Control OUT
bus
DO D Q
Data
bus 5 V
E Q Inverting R
driver
D Flop-flop LED
FIGURE 5.49: Interface circuit between a digital computer and discrete input and discrete
output devices. A R-S flip-flop is used to eliminate the debouncing problem of the switch. The D
flip-flop is so that the data is maintained at the output of the flip-flop even when this device is
no longer addressed.

V
CC2
V CC1

R
R 1
2

FIGURE 5.50: ON/OFF control
– of a relay through an
Data Bus - bit n M
opto-coupler and transistor.
Data bus-bit-n output in this
circuit can come from a circuit
as shown in Figure 5.49.