CDC3205G-C Micronas, CDC3205G-C Datasheet - Page 77

• Manufacturer Part Number: CDC3205G-C
• Description: Automotive Controller Family The Device is a Microcontroller For Use in Automotive Applications.the On-chip Cpu is an Arm Processor ARM7TDMI with 32-bit Data And Address Bus, Which Supports Thumb format Instructions.
• Manufacturer: Micronas

PRELIMINARY DATA SHEET
Fig. 7–4:
7.4. Operation of RTC Module
7.4.1. Reset
With the exception of the oscillators, which are enabled by
every reset (OSC.RC = OSC.XM = 1), most parts of the logic
will never be reset. This means, that after every reset the
unneeded oscillator has to be switched off. Further, the
whole logic has to be initialized after a power on reset.
An application that doesn’t want to use RTC and Polling
module can inhibit the outputs of the modules by writing a 2
to OSC.SRC, a 0 to OSC.RC, a 1 to OSC.LD and a 0 to
RTCC.SEL after every reset. This setting also minimizes the
power consumption.
7.4.2. Oscillator Source and Sub Second Counter
The Sub Second Counter SSC generates a 1Hz output sig-
nal at underflow (0x00000 to 0xFFFFF). This signal loads the
SSC with the content of the SSR register and switches the
oscillator source select multiplexer to the desired oscillator
according to the SRC field in the OSC register. This load sig-
nal can be forced by writing a one to flag LD in register OSC.
There are three necessities when to change SSR and
OSC.SRC:
– Starting the SSC for the first time (after power on)
Micronas
WAKE_RES
Because OSC.SRC is not reset by HW, an oscillator
source must be selected and enabled. The SSR has to be
loaded with the reload value necessary for a 1Hz output
RESCORE
RESPORT
RESINT_5
RESETQ
WKST_5
IDLE_5
RES_5
UV
V
CLS
DD
DD
Switching to WAKE/STANDBY and IDLE and Wake-up
CPU
CPU
June 12, 2003; 6251-579-1PD
– Changing the SSR
– Changing the oscillator source
Precaution: Changing the oscillator source may cause a
fragmentary clock pulse. This may result in wrong SSC and/
frequency. Writing the desired oscillator source in field
SRC, enabling it if necessary and setting flag LD in regis-
ter OSC immediately selects the new oscillator source
and loads SSR to SSC.
Due to temperature or other dependencies of the oscilla-
tor it may be necessary to adjust the reload value in the
SSR register from time to time. This can be done within
the RTC interrupt service routine. Write the new reload
value to the SSR register. Make sure that this will be com-
pleted before the next underflow of the SSC, which simul-
taneously loads the SSC with the new SSR value and
also switches the oscillator source with the beginning of
the next second.
Due to switching to a power saving mode it may be neces-
sary to change the oscillator source. This can be done
within the RTC interrupt service routine. Select the
desired oscillator source in OSC.SRC and write the corre-
sponding reload value to the SSR register. Make sure that
both will be completed before the next underflow of the
SSC, which simultaneously loads the new SSR value to
the SSC and switches to the new oscillator source with
the beginning of the next second.
2048 Clk
CDC 32xxG-C
75