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528
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 8:
Timer Resources
R
(TCR[ARE]=1).
•
If auto-reload mode is disabled (TCR[ARE]=0), the PIT decrements from 1 to 0. When
the PIT contains a value of 0, it stops decrementing until software loads it with a non-
zero value.
Auto-reload mode is disabled after a reset.
Timer-Control Register
The timer-control register (TCR) is a 32-bit register used to control the PPC405 timer
events.
shows the format of the TCR. The fields in TCR are defined as shown in
The TCR is a privileged SPR with an address of 986 (0x3DA). It is read and written using
the
mfspr
and
mtspr
instructions.
0
1
2
3
4
5
6
7
8
9
10
31
WP
WRC
WIE PIE
FP
FIE ARE
Figure 8-4:
Timer-Control Register (TCR)
Table 8-3:
Timer-Control Register (TCR) Field Definitions
Bit
Name
Function
Description
0:1
WP
Watchdog Period
00—2
17
clocks
01—2
21
clocks
10—2
25
clocks
11—2
29
clocks
Specifies the period for a watchdog-timer event.
2:3
WRC
Watchdog Reset Control
00—No reset
01—Processor reset
10—Chip reset
11—System reset
Specifies the type of reset that occurs as a result of a watchdog-
timer event.
After a bit is set in the WRC field, it cannot be cleared by software.
Only a reset can clear the bit. This prevents errant code from
disabling watchdog resets.
4
WIE
Watchdog-Interrupt Enable
0—Disabled
1—Enabled
Enables and disables watchdog interrupts.
5
PIE
PIT-Interrupt Enable
0—Disabled
1—Enabled
Enables and disables programmable-interval timer interrupts.
6:7
FP
FIT Period
00—2
9
clocks
01—2
13
clocks
10—2
17
clocks
11—2
21
clocks
Specifies the period for a fixed-interval timer event.
8
FIE
FIT-Interrupt Enable
0—Disabled
1—Enabled
Enables and disables fixed-interval timer interrupts.
9
ARE
Auto-Reload Enable
0—Disabled
1—Enabled
Enables and disables the programmable-interval timer auto-reload
mode.
10:31
Reserved
Содержание Virtex-II Pro PPC405
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