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2-78
Computer Group Literature Center Web Site
Raven PCI Host Bridge & Multi-Processor Interrupt Controller Chip
2
BC
BASE COUNT. This field contains the 31 bit count for
this timer. When a value is written into this register and
the CI bit transitions from a 1 to a 0, it is copied into the
corresponding Current Count register and the toggle bit in
the Current Count register is cleared. When the timer
counts down to zero, the Current Count register is
reloaded from the Base Count register.
Timer Vector/Priority Registers
MASK
MASK. Setting this bit disables any further interrupts
from this source. If the mask bit is cleared while the bit
associated with this interrupt is set in the IPR, the interrupt
request will be generated.
ACT
ACTIVITY. The activity bit indicates that an interrupt
has been requested or that it is in-service. The ACT bit is
set to a one when its associated bit in the Interrupt Pending
Register or In-Service Register is set.
PRIOR
Interrupt priority 0 is the lowest and 15 is the highest.
Note that a priority level of 0 will not enable interrupts.
VECTOR This vector is returned when the Interrupt Acknowledge
register is examined upon acknowledgement of the
interrupt associated with this vector.
Offset
Timer 0 - $01120
Timer 1 - $01160
Timer 2 - $011A0
Timer 3 - $011E0
Bit
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0 9 8 7 6 5 4 3 2 1 0
Name
TIMER VECTOR/PRIORITY
M
ASK
ACT
PRIOR
VECTOR
Operation
R/W
R
R
R/W
R
R/W
Reset
1
0
$000
$0
$00
$00