m41t93 STMicroelectronics, m41t93 Datasheet - Page 12

• Manufacturer Part Number: m41t93
• Description: Serial Spi Bus Rtc With Battery Switchover
• Manufacturer: STMicroelectronics

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Operation
The M41T93 clock operates as a slave device on the SPI serial bus. Each memory device is
accessed by a simple serial interface that is SPI bus-compatible. The bus signals are SCL,
SDI, and SDO (see
when the Chip Enable input (E) is held low. All instructions, addresses and data are shifted
serially in and out of the chip. The most significant bit is presented first, with the data input
(SDI) sampled on the first rising edge of the clock (SCL) after the Chip Enable (E) goes low.
The 32 bytes contained in the device can then be accessed sequentially in the following
order:
The M41T93 clock continually monitors V
fall below V
counter. Inputs to the device will not be recognized at this time to prevent erroneous data
from being written to the device from a an out-of-tolerance system.
The power input will also be switched from the V
below the battery back-up switchover voltage (V
will be maintained by the battery supply. As system power returns and V
the battery is disconnected, and the power supply is switched to external V
Write protection continues until V
information on Battery Storage Life refer to Application Note AN1012.
11-15
21-25
26-32
10
16
17
18
19
20
1
2
3
4
5
6
7
8
9
Tenths/hundredths of a second register
Seconds register
Minutes register
Century/hours register
Day register
Date register
Month register
Year register
Digital calibration register
Watchdog register
Alarm1 registers
Flags register
Timer value register
Timer control register
Analog calibration register
Square wave register
Alarm2 registers
User RAM
RST
, the device terminates an access in progress and resets the device address
Table 1 on page 7
CC
reaches V
and
CC
Figure 5 on page
for an out-of tolerance condition. Should V
PFD
CC
SO
pin to the external battery when V
(min) plus t
= V
RST
). At this time the clock registers
10). The device is selected
REC
(min). For more
CC
rises above V
CC
.
CC
CC
falls
SO
,