Bally 5000 Plus, Manual

Page: 89 / 388

3 . MPU BOARD
C i r cu i t Descr i pt i on ( cont ' d )
Powe r down
On
powe r down , U46 p i n 1 r ece i ves
t he l og i c LOW SAFECE s i gna l . U46
I nver t s t he s i gna l and ou t pu t s I t
at p i n 2 to U66 p i n 1 0 . U66 p i n 8
sends t he s i gna l to U66 p i n 1 . U66
p i n 3 sends t he s i gna l to U30 p i n
1 . U30 I s dese l ec t ed . T hen , t he
r ea l t i me c l ock cannot be c hecked
or c hanged .
NOT E S
REAL T I M
E CLOCK
D I AGRAM
3-32
74HC52
U66
./i
5 8274
ADO
A 0 I
A 02
A D )
00
0 I
0
2 U30
F i g . 3-1 2
Y l
3 2 . 7 6 8 K H I
C4
!> · 30
P I