DS1216 SmartWatch RAM/SmartWatch ROM
Figure 1. SmartWatch Comparison Register Definition
7
1
0
1
0
1
0
1
0
0
1
0
1
0
1
0
1
0
HEX
VALUE
C5
3A
A3
5C
C5
3A
A3
5C
BYTE 0
BYTE 1
BYTE 2
BYTE 3
BYTE 4
BYTE 5
BYTE 6
BYTE 7
1
0
0
1
1
0
0
1
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1
0
0
1
1
0
0
1
0
1
1
0
0
1
1
0
NOTE:
THE PATTERN RECOGNITION IN HEX IS C5, 3A, 5C, C5, 3A, A3, 5C. THE ODDS OF THIS PATTERN
ACCIDENTALLY DUPLICATING AND CAUSING INADVERTENT ENTRY TO THE SMARTWATCH ARE LESS
THAN 1 IN 10
19
. THIS PATTERN IS SENT TO THE SMARTWATCH LSB TO MSB.
The DS1216 SmartWatch performs circuit functions required to make a CMOS RAM nonvolatile. First, a
switch is provided to direct power from the battery or V
CC
supply, depending on which voltage is greater.
This switch has a voltage drop of less than 0.2V. The second function that the SmartWatch provides is
power-fail detection, which occurs at V
TP
. The DS1216 constantly monitors the V
CC
supply. When V
CC
goes out of tolerance, a comparator outputs a power-fail signal to the chip-enable logic. The third function
accomplishes write protection by holding the chip-enable signal to the memory within 0.2V of V
CC
or
battery. During nominal power-supply conditions, the memory chip-enable signal will track the chip-
enable signal sent to the socket with a maximum propagation delay of 6ns.
Each DS1216 is shipped from Maxim with its lithium energy source disconnected, ensuring full energy
capacity. When V
CC
is first applied at a level greater than the lithium energy source is enabled for battery-
backup operation.
NONVOLATILE CONTROLLER OPERATION
FRESHNESS SEAL
5 of 15
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