Register Model
PowerPC e500 Core Family Reference Manual, Rev. 1
Freescale Semiconductor
2-15
•
The watchdog timer, also a selected TB bit, provides a way to signal a critical exception
when the selected bit transitions from 0 to 1. It is typically used for system error recovery.
If software does not respond in time to the initial interrupt by clearing the associated status
bits in the TSR before the next expiration of the watchdog timer interval, a watchdog
timer-generated processor reset may result, if so enabled.
All timer facilities must be initialized during start-up.
2.6.1
Timer Control Register (TCR)
The e500 implements the TCR, shown in
Figure 2-6
, as defined by the Book E architecture except
as follows:
•
TCR[WPEXT] and TCR[FPEXT], not specified in Book E, are concatenated with
TCR[WP] and TCR[FP] to select a bit that triggers the watchpoint timer and fixed-interval
timer events.
•
The value programmed into WRC is reflected on the e500 wrs signals.
Table 2-5
describes the e500 TCR fields that differ from the Book E definition.
SPR 340
Access: Supervisor-only
32
33
34
35
36
37
38 39
40
41
42 43
46 47
50 51
63
R
WP
WRC WIE DIE
FP
FIE ARE —
WPEXT
FPEXT
—
W
Reset
All zeros
Figure 2-6. Timer Control Register (TCR)
Table 2-5. TCR Implementation-Specific Field Descriptions
Bits
Name
Description
32–33
WP
Watchdog timer period. When concatenated with WPEXT, specifies one of 64-bit locations of the time base
used to signal a watchdog timer exception on a transition from 0 to 1.
WPEXT,WP = 0000_00 selects TBU[32] (the msb of the TB)
WPEXT,WP = 1111_11 selects TBL[63] (the lsb of the TB)
34–35
WRC
Watchdog timer reset control. When a watchdog reset event occurs, the value programmed into WRC is
reflected on
wrs and into TSR[WRS], but the WRC bits are reset to 00. At this point, software can reprogram
WRC. Although WRC can be set by software, it cannot be cleared by software (except by a software-induced
reset). Once written to a non-zero value, WRC may no longer be altered by software.
00 No watchdog timer reset will occur.
01 Force processor checkstop on second timeout of watchdog timer
10 Assert processor reset output (
p_resetout_b) on second timeout of watchdog timer
11 Reserved
38–39
FP
Fixed interval timer period. When concatenated with FPEXT, FP specifies one of 64 bit locations of the time
base used to signal a fixed-interval timer exception on a transition from 0 to 1.
FPEXT || FP = 0000_00 selects TBU[32] (the msb of the TB)
FPEXT || FP = 1111_11 selects TBL[63] (the lsb of the TB)
Содержание PowerPC e500 Core
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Страница 440: ...PowerPC e500 Core Family Reference Manual Rev 1 A 8 Freescale Semiconductor Programming Examples...
Страница 444: ...PowerPC e500 Core Family Reference Manual Rev 1 B 4 Freescale Semiconductor Guidelines for 32 Bit Book E...
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