DS1685/DS1687 3V/5V Real-Time Clocks
Figure 4. Update-Ended And Periodic-Interrupt Relationship
1 second
UIP
tBUC
UF
PF
tPI/2
tPI/2
tPI = PERIODIC INTERRUPT TIME INTERNAL PER TABLE 3.
tBUC = DELAY BEFORE UPDATE CYCLE = 244µs.
EXTENDED FUNCTIONS
The extended functions provided by the DS1685/DS1687 that are new to the RAMified RTC family are accessed by
a software-controlled bank-switching scheme, as illustrated in Figure 5. In bank 0, the clock/calendar registers and
50 bytes of user RAM are in the same locations as for the DS1287. As a result, existing routines implemented
within BIOS, DOS, or application software packages can gain access to the DS1685/DS1687 clock registers with
no changes. Also in bank 0, an extra 64 bytes of RAM are provided at addresses just above the original locations
for a total of 114 directly addressable bytes of user RAM.
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DALLAS [ DALLAS SEMICONDUCTOR ]
