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10006024-04 Katana
®
752i User’s Manual
7-1
Section 7
Real-Time Clock
The processor complex on the Katana
®
752i has a standard real-time clock (RTC), consisting
of an M41T00 device from STMicroelectronics. The M41T00 has an integrated year-2000-
compatible RTC, power sense circuitry, and uses eight bytes of non-volatile RAM for the
clock/calendar function. It is powered from the
+3.3 volt rail during normal operation. The M41T00 device connects to an I
2
C bus (see
page 5-8). The M41T00 device is backed up by power from a single, super capacitor, which
will hold a charge for at least two hours.
BLOCK DIAGRAM
The following block diagram shows the basic structure of the M41T00 device.
Figure 7-1: M41T00 Real-Time Clock Block Diagram
OPERATION
The M41T00 clock operates as a slave device on the serial bus. To obtain access, the RTC
implements a start condition followed by the correct slave address (D0
16
). Access the eight
bytes in the following order:
Seconds
Minutes
Century/Hours
Day
Date
Month
Year
Control
1Hz
OSC1
OSC0
FT/OUT
SCL
SDA
V
CC
V
SS
V
BAT
Address
Register
Control
Logic
Divider
Oscillator
32.768 KHz
Voltage
Sense and
Switch
Circuitry
Serial
Bus
Interface