– 85 –
11. Reset Circuit
●
Reset circuit performs initial setting of the microcomputer program before power is turned on.
●
Microcomputer resets program with reset voltage set to Lo, and program can be operated with Hi.
●
Fig. 11-1 shows the reset circuit and Fig. 11-2 shows waveform at each point when power is turned on
and off.
●
When power is turned on, 12V line and 5V line voltages rise and 12V line voltage reaches 7.2V (Zenor
voltage of ZD501), ZD301 is turned ON, Q2 and Q3 are turned ON and reset voltage input to pin
&
of
microcomputer is set to Hi. By ZD501, reset voltage maintains input of pin
&
at L
0
until V
DD
of microcomputer
rises to 5V to obtain operable status.
●
When power is shut off and potential of 12V is lowered, ZD501 is shifted to OFF. However, since reset
voltage is feed back to Q2 by R4, Q2 maintains ON state until 12V line voltage drops to about 7.6V. This
prevents reset voltage from chattering due to voltage change in 12V line.
12
6
0
12
6
0
12V line
5V line
12V line
5V line
Reset voltage
Reset voltage
Fig. 11-2
Time
Time
P
o
w
er is ON
V
oltage
(V)
P
o
w
er is OFF
V
oltage
(V)
2
1
17
0V
0V
0V
0V
5V
Q3
Q2
R4
R232
12V
ZD301
HIC-1
Micro computer
AX-8E21
RESET
Normal: Hi
Reset:
Lo
Fig. 11-1
Содержание RAC-25CNH11
Страница 35: ... 35 CIRCUIT DIAGRAM MODEL RAS 25CNH11 ...
Страница 36: ... 37 CIRCUIT DIAGRAM MODEL RAC 25CNH11 ...
Страница 104: ... 113 PARTS LIST AND DIAGRAM MODEL RAS 25CNH11 11 2 18 8 20 19 12 63 1 4 60 3 7 14 15 6 5 16 13 88 61 17 9 62 10 ...
Страница 106: ... 115 MODEL RAC 25CNH11 55 22 59 16 26 24 23 20 21 19 13 52 58 53 56 57 2 3 51 15 14 18 4 5 9 6 8 54 17 7 11 10 12 25 ...
Страница 108: ...RAS 25CNH11 RAC 25CNH11 PM NO 0164E Printed in Malaysia HITACHI ...