
Agere Systems Inc.
41
Data Sheet
July 2001
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
4 Reset/Clock Management
(continued)
Table 14. Reset Peripheral Control (Read, Clear, Set) Register
s
Note: This register is initialized to all zeros on reset except for the
ERS
(bit 0), which is set to 1 upon reset.
4.2.11 RTC External Divider Register
The
RTC external divider register
allows the 11.52 MHz external clock (
EXT_CLK
) to be divided down to pro-
duce a pseudo real-time clock in applications where a real-time crystal and real-time accuracy are not needed. The
RTC
external divider register
is a 16-bit register whose value is loaded into a down counter every time the down
counter reaches 0. There is a toggle flip-flop that changes state whenever the counter reaches 0. The output clock
rate is given by the following equation:
EXT_PROG_CLK = EXT_CLK/ECD/2.
For a pseudo real-time clock of 32727.27 Hz the programmed value for
ECD
becomes 176 (0xB0).
Table 15 shows the format of the
RTC external divider register
.
Address—Read 0xE000 0040, Clear 0xE000 0044, Set 0xE000 0048
17
16
EREP
RSVD
10
9
IrDA
USB
3
2
RSVD
ITIMR
Bit #
Name
Bit #
Name
Bit #
Name
Bit #
31: 18
17
16
15
14
13
12
11
10
9
8
7
6
5
4:3
2
1
0
31:18
RSVD
11
UART
4
RSVD
Name
RSVD
EREP
RSVD
EMAC
DCC
KLC
RTC
UART
IrDA
USB
PIO
SSI
DMA
INTC
RSVD
ITIMR
RSVD
ERS
15
14
DCC
7
SSI
0
ERS
13
KLC
6
DMA
—
—
12
RTC
5
INTC
—
—
EMAC
8
PIO
1
RSVD
Description
Reserved.
Ethernet repeater circuit.
Reserved
.
Ethernet MAC.
DSP communications controller.
Key and lamp controller.
Real-time clock controller.
Asynchronous communications controller channel 1 to UART adjunct.
Asynchronous communications controller channel 0 to IrDA receiver.
Universal serial bus controller.
Parallel input output controller.
Synchronous serial input output controller.
Direct memory access controller.
Interrupt controller.
Reserved.
Interval and watchdog timer.
Reserved.
External reset bit, (
RTS0N
).