DS17285(1998) View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated

Part Name

Description

Manufacturer

DS17285
(Rev.:1998)

3 Volt/5 Volt Real Time Clock

Dallas Semiconductor -> Maxim Integrated 

DS17285/DS17287

The RTC address is latched on the falling edge of the

ALE signal. Each time an RTC address is latched, the

register address stack is pushed. The stack is only four

registers deep, holding the three previous RTC

addresses in addition to the current RTC address being

accessed. The following waveform illustrates how the

BIOS could recover the RTC address when an SMI

occurs.

ALE

1

2

3

4

1. The RTC address is latched.

2. An SMI is generated before an RTC read or write occurs.

3. RTC address 0Ah is latched and the address from “1” is pushed to the “RTC Address – 1” stack location.

This step is necessary to change the bank select bit, DV0=1.

4. RTC address 4Eh is latched and the address from “1” is pushed to location 4Eh, “RTC Address – 2” while 0Ah is

pushed to the “RTC Address – 1” location. The data in this register, 4Eh, is the RTC address lost due to the SMI.

030598 18/32

Share Link: