Motorola MC68VZ328 Manuale Utente

11-10

The real-time clock control (RTCCTL) register is used to enable the real-time clock and provide reference 
frequency information to the prescaler. The settings for the RTCCTL register are described in Table 11-7.

RTC Control Register

The real-time clock interrupt status register (RTCISR) indicates the status of the various real-time clock 
interrupts. Each bit is set when the corresponding event occurs. You must clear these bits by writing ones, 
which also clears the interrupt. This register can post interrupts while the system clock is idle or in sleep 
mode. The settings for the RTCISR register are described in Table 11-8 on page 11-11. For more 
information about the frequency of the RTC interrupts, refer to Table 11-9 on page 11-12.

BIT 

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

BIT 

0

RTCEN

REFREQ

TYPE

rw

rw

RESET

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0x0080

Reserved
Bits 15–8

Reserved

These bits are reserved and should be set to 
0.

RTCEN
Bit 7

Real-Time Clock Enable—This bit, when set, 
enables the real-time clock.

0 = Disable the real-time clock
1 = Enable the real-time clock (default)

Reserved
Bit 6

Reserved

This bit is reserved and should be set to 0.

REFREQ
Bit 5

Reference Frequency—This bit is set to the fre-
quency of the crystal oscillator.

0 = Reference frequency is 32.768 kHz 

(default).

1 = Reference frequency is 38.4 kHz.

Reserved
Bits 4–0

Reserved

These bits are reserved and should be set to 
0.