
Timing System
Pulse Accumulator
MC68HC11E Family
—
Rev. 4
Technical Data
MOTOROLA
Timing System
207
9.8.3 Pulse Accumulator Status and Interrupt Bits
The pulse accumulator control bits, PAOVI and PAII, PAOVF and PAIF,
are located within timer registers TMSK2 and TFLG2.
PAOVI and PAOVF
—
Pulse Accumulator Interrupt Enable
and Overflow Flag
The PAOVF status bit is set each time the pulse accumulator count
rolls over from $FF to $00. To clear this status bit, write a 1 in the
corresponding data bit position (bit 5) of the TFLG2 register. The
PAOVI control bit allows configuring the pulse accumulator overflow
for polled or interrupt-driven operation and does not affect the state of
PAOVF. When PAOVI is 0, pulse accumulator overflow interrupts are
inhibited, and the system operates in a polled mode, which requires
that PAOVF be polled by user software to determine when an
overflow has occurred. When the PAOVI control bit is set, a hardware
Address:
$1024
Bit 7
6
5
4
3
2
1
Bit 0
Read:
TOI
RTII
PAOVI
PAII
PR1
PR0
Write:
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-27. Timer Interrupt Mask 2 Register (TMSK2)
Address:
$1025
Bit 7
6
5
4
3
2
1
Bit 0
Read:
TOF
RTIF
PAOVF
PAIF
Write:
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-28. Timer Interrupt Flag 2 Register (TFLG2)