DS1602 Datasheet, PDF (3/10 Pages) Dallas Semiconductor – Elapsed Time Counter

DS1602
goes to a high impedance state. RST should only be transitioned low while the clock is high to avoid
disturbing the last bit of data. All data transfers must consist of 8 bits when transferring protocol only or 8
+ 32 bits when reading or writing either counter. Data transfer is illustrated in Figure 3.
DATA INPUT
Following the 8–bit protocol that inputs write mode, 32 bits of data are written to the selected counter on
the rising edge of the next 32 CLK cycles. After 32 bits have been entered any additional CLK cycles will
be ignored until RST is transitioned low to end data transfer, and then high again to begin new data
transfer.
DATA OUTPUT
Following the eight CLK cycles that input read mode protocol, 32 bits of data will be output from the
selected counter on the next 32 CLK cycles. The first data bit to be transmitted from the selected 32–bit
counter occurs on the falling edge after the last bit of protocol is written. When transmitting data from
the selected 32–bit counter, RST must remain at high level as a transition to low level will terminate data
transfer. Data is driven out the DQ pin as long as CLK is low. When CLK is high the DQ pin is tristated.
CRYSTAL SELECTION
A standard 32.768 kHz quartz crystal can be directly connected to the DS1602 via pins 1 and 2 (X1, X2).
The crystal selected for use should have a specified load capacitance (C_L) of 6 pF. For more information
on crystal selection and crystal layout considerations, please consult Application Note 58, “Crystal
Considerations with Dallas Real Time Clocks.”
BATTERY SELECTION
The battery selected for use with the DS1602 should have an output voltage between 2.5 and 3.5 volts. A
lithium battery of 35 mAh or greater will run the elapsed time counter for over 10 years in the absence of
power. Small lithium coin cell batteries produce both the proper output voltage and have the capacity to
supply the DS1602 for the useable lifetime of the equipment where they are installed.
DS1602 ELAPSED TIME COUNTER BLOCK DIAGRAM Figure 1
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