DS1216 Datasheet, PDF (5/15 Pages) Dallas Semiconductor – SmartWatch RAM DS1216B/C/D/H SmartWatch ROM DS1216E/F

DS1216 SmartWatch RAM/SmartWatch ROM
Figure 1. SmartWatch Comparison Register Definition
7
BYTE 0
11
0
0
0
1
BYTE 1
00
1
1
1
0
0
0
1
1
0
HEX
VALUE
C5
3A
BYTE 2
10
1
0
0
0
1
1
A3
BYTE 3
01
0
1
1
1
0
0
5C
BYTE 4
11
0
0
0
1
0
1
C5
BYTE 5
00
1
1
1
0
1
0
3A
BYTE 6
10
1
0
0
0
1
1
A3
BYTE 7
01
0
1
1
1
0
0
5C
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 10¹⁹. THIS PATTERN IS SENT TO THE SMARTWATCH LSB TO MSB.
NONVOLATILE CONTROLLER OPERATION
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.
FRESHNESS SEAL
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.
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