MC68HC11F1_13 Datasheet, PDF (124/158 Pages) Freescale Semiconductor, Inc – Technical Data

Freescale Semiconductor, Inc.
9.6.3 Pulse Accumulator Status and Interrupt Bits
The pulse accumulator control bits, PAOVI, PAII, PAOVF, and PAIF are located within
timer registers TMSK2 and TFLG2.
TMSK2 — Timer Interrupt Mask 2 Register
Bit 7
6
5
4
3
TOI
RTII
PAOVI
PAII
—
RESET:
0
0
0
0
0
$1024
2
1
Bit 0
—
PR1
PR0
0
0
0
TFLG2 — Timer Interrupt Flag 2 Register
$1025
Bit 7
6
5
4
3
2
1
Bit 0
TOF
RTIF PAOVF PAIF
—
—
—
—
RESET:
0
0
0
0
0
0
0
0
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 one 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 zero, 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 interrupt request is generated each time PAOVF is set. Before leaving
the interrupt service routine, software must clear PAOVF by writing to the TFLG2 reg-
ister.
PAII and PAIF — Pulse Accumulator Input Edge Interrupt Enable and Flag
The PAIF status bit is automatically set each time a selected edge is detected at the
PA7/PAI/OC1 pin. To clear this status bit, write to the TFLG2 register with a one in the
corresponding data bit position (bit 4). The PAII control bit allows configuring the pulse
accumulator input edge detect for polled or interrupt-driven operation but does not af-
fect setting or clearing the PAIF bit. When PAII is zero, pulse accumulator input inter-
rupts are inhibited, and the system operates in a polled mode. In this mode, the PAIF
bit must be polled by user software to determine when an edge has occurred. When
the PAII control bit is set, a hardware interrupt request is generated each time PAIF is
set. Before leaving the interrupt service routine, software must clear PAIF by writing to
the TFLG2 register.
9-18
TIMING SYSTEM
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MC68HC11F1
TECHNICAL DATA