st10f269z1 STMicroelectronics, st10f269z1 Datasheet - Page 105

• Manufacturer Part Number: st10f269z1
• Description: St10f269 16-bit Mcu With Mac Unit, 256k Byte Flash Memory And 12k Byte Ram
• Manufacturer: STMicroelectronics

ST10F269
16 - REAL TIME CLOCK
The Real Time Clock is an independent timer,
which clock is directly derived from the clock
oscillator on XTAL1 input so that it can keep on
running even in Idle or Power down mode (if
enabled to). Registers access is implemented
onto the XBUS. This module is designed for the
following purposes:
– Generate the current time and date for the system
– Cyclic time based interrupt, provides Port
– 58-bit timer for long term measurement
– Capable to exit the ST10 chip from power down
The real time clock is base on two main blocks of
counters. The first block is a prescaler which
generates a basic reference clock (for example a
1 second period). This basic reference clock is
coming out of a 20-bit DIVIDER (4-bit MSB
RTCDH counter and 16-bit LSB RTCDL counter).
This 20-bit counter is driven by an input clock
derived from the on-chip high frequency CPU
clock, predivided by a 1/64 fixed counter (see
Figure 51). This 20-bit counter is loaded at each
basic reference clock period with the value of the
Figure 50 : ESFRs and Port Pins Associated with the RTC
2 external interrupts every second and every
n seconds (n is programmable) if enabled.
mode (if PWDCFG of SYSCON set) after a pro-
grammed delay.
EXISEL External Interrupt Source Selection register (Port 2)
1 second timed interrupt request (RTCSI) triggers firq[2] and alarm interrupt request (RTCAI) triggers firq[3]
RTC data and control registers are implemented onto the XBUS.
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EXISEL
20-bit PRESCALER register (4-bit MSB RTCPH
register and 16-bit LSB RTCPL register). The
value of the 20-bit RTCP register determines the
period of the basic reference clock.
A timed interrupt request (RTCSI) may be sent on
each basic reference clock period. The second
block of the RTC is a 32-bit counter (16-bit RTCH
and 16-bit RTCL). This counter may be initialized
with the current system time. RTCH/RTCL counter
is driven with the basic reference clock signal. In
order to provide an alarm function the contents of
RTCH/RTCL counter is compared with a 32-bit
alarm register (16-bit RTCAH register and 16-bit
RTCAL register). The alarm register may be
loaded with a reference date. An alarm interrupt
request (RTCAI), may be generated when the
value of RTCH/RTCL counter matches the
reference date of RTCAH/RTCAL register.
The timed RTCSI and the alarm RTCAI interrupt
requests can trigger a fast external interrupt via
EXISEL register of port 2 and wake-up the ST10
chip when running power down mode. Using the
RTCOFF bit of RTCCON register, the user may
switch off the clock oscillator when entering the
power down mode.
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CCxIC
16 - REAL TIME CLOCK
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