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Real time clock with ST7 Timer Output Compare

Figure 1. Output Compare Register Update Flowchart

with the Output compare register offset value (OCxHR, OCxLR).

3 REAL TIME CLOCK APPLICATION

The real time clock application is based on four software counters (100ms, seconds, minutes

and hours) updated by a 100ms ST7 timer output compare 1 interrupt.

Time Base [ms]

2

10

20

50

100

131.07

OCxHR OCxLR offset [hex]

03E8

1388

2710

61A8

C350

FFFF

STORE OCxHR AND OCxLR REGISTER

VALUES IN TEMPORARY REGISTERS

UPDATE OCxHR AND OCxLR VALUES

THROUGH TEMPORARY REGISTERS

STORE NEW OCxHR REGISTER VALUE

STORE NEW OCxLR REGISTER VALUE

2

(cc1,cc0)

=

8

4 MHz

= 500 KHz

TimeBase

=

TimeBase

2 us