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Operating System Timers
Copyright © 12/13/06 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006
Document Classification: Proprietary Information
Page 423
Not approved by Document Control. For review only.
OSMR4 - OSMR11 are compared against an OS Counter register after every rising edge of the clock selected by
OMCR[CRES[3]] and OMCR[CRES] of the appropriate OS Match Control register (see
).
If any of these registers match the selected counter register and the corresponding interrupt-enable bit is set in the
OIER register, the corresponding status bit in the OSSR is set. The status bits are routed to the interrupt controller
where they generate a CPU interrupt if the corresponding interrupt mask bits in the interrupt controller are
enabled.
These are read/write registers. Ignore reads from reserved bits. Write 0b0 to reserved bits.
14.5.3
OS Timer Watchdog Match Enable Register (OWER)
OSCR0 can be programmed to generate a watchdog-reset signal. OSCR0 is compared to OSMR3 every rising
edge of the 3.25 MHz clock. When OWER[WME] is set, and if a match is detected, the output pin WDOG_RST
is set, and a reset is applied to the processor with most of internal states to be cleared.
Follow this procedure when using OSMR3 as a watchdog timer:
•
Each time the operating system services the register, read the current value of the counter and add a number
to the value read. The number added corresponds to the amount of time before the next timeout. Remember
to account for counter wraparound when doing these calculations.
•
Write this number back to OSMR3.
•
The OS must repeat this procedure periodically to correctly prevent a match from occurring. If a match
occurs, the OS timer asserts the watchdog reset.
The Watchdog-Enable register contains a single control bit, (WME), that enables the watchdog function when
software writes a 0b1 to this bit. Once enabled, the watchdog function can be disabled only by one of the reset
functions (hardware, sleep, watchdog, or GPIO). Writing a zero to the enable bit after it has been set has no
effect.
shows the bit locations for the OWER register.
Table 14-5. OSMR0–11 Bit Definitions
0x40A0_0000
0x40A0_0004
0x40A0_0008
0x40A0_000C
0x40A0_0080
0x40A0_0084
0x40A0_0088
0x40A0_008C
0x40A0_0090
0x40A0_0094
0x40A0_0098
0x40A0_009C
OSMR0
OSMR1
OSMR2
OSMR3
OSMR4
OSMR5
OSMR6
OSMR7
OSMR8
OSMR9
OSMR10
OSMR11
OS Timers
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
Match_Value
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bits
Access
Name
Description
31:0
R/W
Match_Value
Match Value
The value that is compared with OSCRx.