Clock Module
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
6-16 Freescale Semiconductor

6.7.1.10 Backup Watchdog Timer Control Register (BWCR)

The BWCR is used to configure the interaction between the clock module and the Backup W atchdog T imer

module (see Chapter 7, “Backup Watchdog Timer (BWT) Module”).

NOTE

The BWCR is a write-once register. The contents of this register are

preserved during a warm reset. This register is reset only by a Power-on

Reset event.

2
REFS
Reference Source bit. This bit configures the RTC oscillator for operation with an external crystal or external
oscillator.
0 RTC oscillator is running in external oscillator mode.
1 RTC oscillator is running in external crystal mode.
1
LPEN
Low-Power Enable bit. This bit configures the RTC oscillator to run in low-power mode when using an
external crystal.
0 RTC oscillator runs in normal-power mode.
1 RTC oscillator runs in low-power mode.
0
RTCSEL
RTC source selection bit. This bit configures the source of the RTC clock.
0 Source is the system clock.
1 Source is the RTC oscillator.
IPSBAR
Offset: 0x12_0013 (BWCR)
Access: Supervisor read/write
76543210
R——————
BWDSTOP BWDSEL
W
Reset1:
1The BWCR is reset to these values only after a Power-On Reset. The register contents are preserved during a warm
reset.
00000000

Figure 6-11. Backup Watchdog Timer Control Register (BWCR)

Table 6-15. BWCR Field Descriptions

Field Description
7–2 Reserved, should be cleared.

Table 6-14. RTCCR Field Descriptions (continued)

Field Description