
Agere Systems Inc.
43
Data Sheet
July 2001
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
4 Reset/Clock Management
(continued)
Table 16. RTC Clock Prescale Registers
(continued)
4.2.13 RTC Control Register
The
RTC control register
selects the real-time clock source and enables the RTC counters. Table 17 shows the
format of the
RTC control register
.
Table 17. RTC Control Register
Bit #
1
Name
D3
Description
Indicates that the prescaler input is divided by 3.
If 1, divide the clock by 3.
If 0, do not divide the clock by 3.
Indicates that the prescaler input is divided by 2.
0
D2
If 1, divide the clock by 2.
If 0, do not divide the clock by 2.
Address 0xE000 C000
4
RSVD
BYP
Bit #
Name
Bit #
31:8
31:8
RSVD
Name
RSVD
ENA
7
6:5
3
2
1
IE
0
ENA
RSVD
Description
RSVD
CS
Reserved.
Crystal oscillator enable. Enables the analog portion of the crystal oscillator.
7
If 1, the analog portion of the crystal oscillator is active and using current.
If 0, the analog portion of the crystal oscillator is not active and is not using current.
This bit is set to 0 if the RTC is not being used or bypass mode is set.
This bit is set to 1 on reset.
These bits are set to 11 on reset.
Bypass mode. Bypasses the crystal oscillator circuit.
6:5
4
RSVD
BYP
If 1, a crystal is connected between pins
XRTC0
and
XRTC1
.
If 0, the CMOS clock on pin
XRTC0
is used directly as the clock input.
This bit is set to 0 on reset.
Reserved.
Increment enable. Enables incrementing the
RTC divider register
(see Table 20 on page 45)
.
3:2
1
RSVD
IE
If 1, increment of the
RTC divider register
is enabled.
If 0, increment of the
RTC divider register
is disabled.
This bit is reset to 0 on powerup.
Clock select. Selects the clock source for the
RTC divider register
(see Table 20 on page 45)
.
0
CS
If 1, the clock is from the crystal, or an external CMOS clock.
If 0, the clock is the divided
SYSTEM_CLK
.
This bit is reset to 1 on powerup.