DS1685-3_12 MAXIM [Maxim Integrated Products], DS1685-3_12 Datasheet - Page 17

• Manufacturer Part Number: DS1685-3_12
• Description: 3V/5V Real-Time Clocks
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 4. Update-Ended And Periodic-Interrupt Relationship
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.
UIP
PF
UF
t
t
PI
BUC
= PERIODIC INTERRUPT TIME INTERNAL PER TABLE 3.
= DELAY BEFORE UPDATE CYCLE = 244µs.
t
BUC
17 of 34
1 second
t
PI
t
PI/2
t
PI/2