
80C196KB USER’S GUIDE
RESET CIRCUITS
The simplest way to reset an 80C196KB is to insert a
capacitor between the RESET pin and V
SS
. The
80C196KB has an internal pullup which has a value
between 6K and 50K ohms. A 5 uF or greater capaci-
tor should provide sufficient reset time as long as Vcc
rises quickly.
Figure 13-7 shows what the RESET pin looks like in-
ternally. The RESET pin functions as an input and as
an output to reset an entire system with a watchdog
timer overflow, or by executing a RST instruction. For
a system reset application, the reset circuit should be a
one-shot with an open collector output. The reset pulse
may have to be lengthened and buffered since RESET
is only asserted for four state times. If this is done, it is
possible for the 80C196KB to start running before oth-
er chips in the system are out of reset. Software must
take this condition into account. A capacitor cannot be
connected directly to RESET if it is to drive the reset
pins of other chips in the circuit. The capacitor may
keep the voltage on the pin from going below guaran-
teed V
IL
for circuits connected to the RESET pin. Fig-
ure 13-8 shows an example of a system reset circuit.
13.5 Minimum Hardware Connections
Figure 13-9 shows the minimum connections needed to
get the 80C196KB up and running. It is important to
tie all unused inputs to V
CC
or V
SS
. If these pins are
270651 – 46
Figure 13-7. Reset Pin
270651 – 47
NOTE:
1. The diode will provide a faster cycle time repetitive power-on-resets.
Figure 13-8. System Reset Circuit
68
数控原理与维修
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Содержание 80C196KB Series
Страница 1: ...November 1990 80C196KB User s Guide Order Number 270651 003 http www agreenleaf cn...
Страница 59: ...80C196KB USER S GUIDE Figure 11 7 Ideal A D Characteristic 270651 37 55 http www agreenleaf cn...
Страница 60: ...80C196KB USER S GUIDE Figure 11 8 Actual and Ideal Characteristics 270651 38 56 http www agreenleaf cn...
Страница 61: ...80C196KB USER S GUIDE Figure 11 9 Terminal Based Characteristic 270651 39 57 http www agreenleaf cn...
Страница 70: ...80C196KB USER S GUIDE Figure 13 5 Reset Sequence 80C196KB Reset Sequence 270651 45 66 http www agreenleaf cn...
Страница 83: ...80C196KB USER S GUIDE 270651 80 Figure 15 14 AC Timing Diagrams 79 http www agreenleaf cn...
Страница 84: ...80C196KB USER S GUIDE 270651 81 270651 84 Figure 15 14 AC Timing Diagrams Continued 80 http www agreenleaf cn...