M48T86PC1TR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M48T86PC1TR Datasheet PDF : 36 Pages
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Clock operations
M48T86
should avoid interrupt service routines that would cause the time needed to read valid
time/calendar data to exceed 244 µs.
The third method uses a periodic interrupt to determine if an update cycle is in progress.
The UIP bit is set high between the setting of the PF bit (Register C; Bit 6). Periodic
interrupts that occur at a rate greater than tBUC allow valid time and date information to be
reached at each occurrence of the periodic interrupt.The READs should be completed
within 1/(tPL/2 + tBUC) to ensure that data is not read during the update cycle.
3.9
Square wave output selection
Thirteen of the 15 divider taps are made available to a 1-of-15 selector, as shown in the
block diagram of Figure 4 on page 8. The purpose of selecting a divider tap is to generate a
) square wave output signal on the SQW pin. The RS3-RS0 bits in Register A establish the
t(s square wave output frequency. These frequencies are listed in Table 4 on page 18. The
SQW frequency selection shares the 1-of-15 selector with the periodic interrupt generator.
uc Once the frequency is selected, the output of the SQW pin can be turned on and off under
d program control with the Square Wave Enabled (SQWE) bit.
Pro t(s) Table 4.
lete duc RS3
so ro 0
- Ob te P 0
) le 0
t(s o 0
c bs 0
du O 0
ro ) - 0
P t(s 0
lete uc 1
o d 1
s ro 1
Ob te P 1
le 1
o1
Obs 1
Square wave frequency/periodic interrupt rate
Register A bits
Square wave
RS2
RS1
RS0 Frequency Units
0
0
0
None
0
0
1
256
Hz
0
1
0
128
Hz
0
1
1
8.192
kHz
1
0
0
4.096
kHz
1
0
1
2.048
kHz
1
1
0
1.024
kHz
1
1
1
512
Hz
0
0
0
256
Hz
0
0
1
128
Hz
0
1
0
64
Hz
0
1
1
32
Hz
1
0
0
16
Hz
1
0
1
8
Hz
1
1
0
4
Hz
Periodic interrupt
Period
Units
None
3.90625
ms
7.8125
ms
122.070
us
244.141
us
488.281
us
976.5625
us
1.953125
ms
3.90625
ms
7.8125
ms
15.625
ms
31.25
ms
62.5
ms
125
ms
250
ms
1
1
1
1
2
Hz
500
ms
18/36
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