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Memory Maps and Registers
MVME2500 Installation and Use (6806800L01H)
100
5.6.3 Compare High and Low Word Registers
The tick timer counter is compared to the Compare Register. When the values are equal, the
tick timer interrupt is asserted and the overflow counter increments. If the clear-on-compare
mode is enable, the counter is also cleared. For periodic interrupts, this equation should be
used to calculate the compare value for a specific period (T):
Compare register value=T (us)
When programming the tick timer for periodic interrupt, the counter should be cleared to zero
by software and then enabled. If the counter does not initially start at zero, the time to the first
interrupt may be longer or shorter than expected. Note that the rollover time for the counter
is 71.6 minutes.
Since the processor is 16-bits and the tick timer is 32-bits, the compare register was split in half.
Accessing the whole register will require two transactions.
Table 5-24 Compare High Word Registers
REG
Tick Timer 0 Compare Value High Word - 0xFFC80204
Tick Timer 1 Compare Value High Word - 0xFFC80304
Tick Timer 2 Compare Value High Word - 0xFFC80404
Bit 1514131211109876543210
Field TickTimer Compare Value High Word (16-bits)
OPER R/W
RESET 0x0000
Table 5-25 Compare Low Word Registers
REG
Tick Timer 0 Compare Value Low Word - 0xFFC80206
Tick Timer 1 Compare Value Low Word - 0xFFC80306
Tick Timer 2 Compare Value Low Word - 0xFFC80406
Bit 1514131211109876543210
Field TickTimer Compare Value Low Word (16-bits)
OPER R/W
RESET 0x0000