m41t81 STMicroelectronics, m41t81 Datasheet - Page 19

• Manufacturer Part Number: m41t81
• Description: Serial Access Real-time Clock With Alarms
• Manufacturer: STMicroelectronics

M41T81
3.6
3.7
Square wave output
The M41T81 offers the user a programmable square wave function which is output on the
SQW pin. RS3-RS0 bits located in 13h establish the square wave output frequency. These
frequencies are listed in
completed, the IRQ/FT/OUT/SQW pin can be turned on and off under software control with
the Square Wave Enable Bit (SQWE) located in Register 0Ah.
Table 4.
Century bit
Bits D7 and D6 of Clock Register 03h contain the CENTURY ENABLE Bit (CEB) and the
CENTURY Bit (CB). Setting CEB to a '1' will cause CB to toggle, either from a '0' to '1' or
from '1' to '0' at the turn of the century (depending upon its initial state). If CEB is set to a '0,'
CB will not toggle.
RS3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Square wave output frequency
RS2
Square wave bits
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Table
4. Once the selection of the SQW frequency has been
RS1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
RS0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Frequency
32.768
8.192
4.096
2.048
1.024
None
512
256
128
64
32
16
8
4
2
1
Square wave
Clock operation
Units
kHz
kHz
kHz
kHz
kHz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
-
19/30