Motorola MVME1X7P - Manual (Page 217)

Programming Model
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3
Tick Timer 1 Counter
The Tick Timer 1 Counter is a 32-bit read/write register located at address
$FFF42008. When enabled, it increments every microsecond. Software
may read or write the counter at any time.
Tick Timer 2 Compare Register
The Tick Timer 2 Compare Register is a 32-bit register located at
$FFF4200C. The count value of Tick Timer 2 is compared to this register.
When they are equal, an interrupt is sent to the Local Bus interrupter and
the overflow counter is incremented. If the clear-on-compare mode is
enabled, the counter is also cleared. For periodic interrupts, the following
equation should be used to determine the compare register value for a
specific period.
compare register value = T (
µ
s)
When programming the tick timer for periodic interrupts, 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. The rollover time for the counter is 71.6 minutes.
ADR/SIZ $FFF42008 (32 bits)
BIT 31 . . . 0
NAME Tick Timer 1 Counter
OPER R/W
RESET X
ADR/SIZ $FFF4200C (32 bits)
BIT 31 . . . 0
NAME Tick Timer 2 Compare Register
OPER R/W
RESET 0 P