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Note:
There are three power supplies in the system. VCC0, VCC1 and VCC2.
VCC0 must be present before or at the same time as VCC1.
VCC1 must be present before or at the same time as VCC2.
The RTC and CMOS registers always draw power from VCC0.
VCC2 (Nominal)
Power
Good
BATTERY Voltage >2.5V
Host Register
Access
<4.0
x
Y
N
<4.0 to >4.0
0
Y
N
>4.0
0->1
Y
Timed Lockout
(Note 1)
>4.0
0
Y
N
>4.0
1
Y
Note 1: If VCC2 and VCC1 are powered up at the same time, then the Host Register Access is
delayed by the timed lockout and the 8051 Initialization, whichever is longer.
VCC1 (Nominal)
VCC2 (Nominal)
8051 Initialization
8051 Register
Access
<2.5
x
N
<2.5 to >2.5
x
In Init
N
>2.5
x
In Init
N
>2.5
x
Init Finished
Y