Agere Systems Inc.
73
Data Sheet
July 2001
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
7 Programmable Timers
(continued)
I
Once the watchdog timer function is enabled in the
timer control register
, it cannot be disabled and the watch-
dog timer count rate field (
WTR
) of the
count rate register
cannot be modified.
I
The
WR
bit in the
reset status (control/clear) register
(see Table 13 on page 40)
of the reset and power man-
agement function is set after the microcontroller restarts, if a watchdog timer reset occurred.
I
WTR
of the
timer control register
(see Table 52 on page 76)
is used to determine the effect of reset on the
watchdog timer registers
. If
WTR
is 1, the watchdog timer resets on powerup reset or watchdog reset but is not
affected by the external
reset
pin. If
WTR
is 0, the watchdog timer resets for all three reasons.
I
WIC
of the
timer control register
selects the clock source for the watchdog timer. If 1, the clock source is the
32 kHz clock. If 0, the clock source is the system clock.
Note:
The watchdog timer functionality should be completely set up before switching to the 32 kHz clock.
7.4 Timer Registers
The timer function (interval and watchdog) consists of the registers shown below. All timers depend on the
control
,
status
,
mask
, and
count rate registers
.
.
Table 46. Timer Controller Register Map
Register
Address
Reserved.
Count rate register
(see Table 47 on page 74)
.
WT count register (16-bit counter)
(see Table 49 on page 75)
.
Reserved.
Timer status register
(see Table 50 on page 75)
.
Timer interrupt mask register
(see Table 51 on page 76)
.
Timer control register
(see Table 52 on page 76)
.
IT maximum count register 0 (16-bit counter).
IT count register 0 (16-bit counter).
IT maximum count register 1 (16-bit counter).
IT count register 1 (16-bit counter).
IT maximum count register 2 (16-bit counter).
IT count register 2 (16-bit counter).
IT maximum count register 3 (16-bit counter).
IT count register 3 (16-bit counter).
Reserved.
0xE000 5000—0xE000 5014
0xE000 5018
0xE000 501C
0xE000 5020
0xE000 5024
0xE000 5028
0xE000 502C
0xE000 5030
0xE000 5034
0xE000 5038
0xE000 503C
0xE000 5040
0xE000 5044
0xE000 5048
0xE000 504C
0xE000 5050—0xE000 507F